The smog is due（ ）invisible gases，mostly from automobile exhaust.
题目意为“烟雾是由隐形气体引起的，主要来自汽车尾气。”due to为固定搭配，意为“由于”，后面接名词短语，故选项B正确。
A New Study Says You Can Spread to Your Dog
Research shows that most dog owner's find their pets to be great stress busters.Curling up on the couch with your pug on playing eatch with your Labradoodle is a great way to unwind and letthe cares of the dlay slip away . New science has some bud news for dog owners. Dog might ease your stress. but they can also catch it,
I's an old joke that dogs resemble their owners, but according to this new study out of linkoping universily in sweden . Its actually true in one lecus funny way: stressed out owners have stressedout dog .
To figure this out the researchers took hair samples from 25 border collies and 33 shetland sheepdogs. AS well as their female owners. For both humans and dogs . Hair records the level of the stress bormone cortisol in the body over time s0 by analy zing these hairs, the team could figure out just now much stress both the owners and their pets were under long_ ferm.
The studly found the stress level of the dogs and their owners matched up : higher levels of sitress among owners showed up as higher levels of stress in their dogs. The efct was even more pronounced if the dogs was female or if it took part in agility copettions with is owner.
Previous research has found that cortisol in humans and their dogs can rise together in the short term especially when competing. But this finding was someting new. " This is the first time we've seen a long term synchroniation in stress levels between members of two diferent species。
We haven't scen this between humans and dogs before." lead research lina r oth told the guardian.And what about a pooch's lifestyle?did limited opportunitics for play or more time spent alone stress out the dogs? nearly as much as belonging to a human with high cortisol levels. The personality of the owner seemed to play a role to. Although that varied with the sex of the dog.
Female dogs whose owners had higher scores in the Big five traits of neurotic ism openness, and conscientiousness had higher cortisol levels, while the same was true of male dogs whose owners scored high in agreeableness.
This will not come as a huge surprise to many observant folks who have noticed that highly stung people offen have a highly strung dogs. But should scientifie confrmation of this conection between owners and their dogs put pet if you're arcciety prone? Or if you're under a lot of stress and already a pet owner, should you feel guilty?
Roth replies" 1 don't think you should be anxious that , if you're sressed,, you might harm your dog" instead, your dog is a 8ocial support for you, and you are a social support for the dog.
Your sressede out than made up for by exstra pats , belly rubs, and tennis ball throws.
Though if you do lean towards the anxious side, you might want to think carefully about choosing a resilient type of dog. Just which breeds are best is still an open question.one Roth andher collaborators hope.
It may be possible to match dog and owner in a way that is better for both, from a stress- management says" It may be that certain breeds are not so deeply afected if their owner hasa high sres leve!""
Readers can find answers to the flowin question ecep( )
A New Study Says You Can Spread to Your Dog
Research shows that most dog owner's find their pets to be great stress busters.Curling up on the couch with your pug on playing eatch with your Labradoodle is a great way to unwind and letthe cares of the dlay slip away . New science has some bud news for dog owners. Dog might ease your stress. but they can also catch it,
I's an old joke that dogs resemble their owners, but according to this new study out of linkoping universily in sweden . Its actually true in one lecus funny way: stressed out owners have stressedout dog .
To figure this out the researchers took hair samples from 25 border collies and 33 shetland sheepdogs. AS well as their female owners. For both humans and dogs . Hair records the level of the stress bormone cortisol in the body over time s0 by analy zing these hairs, the team could figure out just now much stress both the owners and their pets were under long_ ferm.
The studly found the stress level of the dogs and their owners matched up : higher levels of sitress among owners showed up as higher levels of stress in their dogs. The efct was even more pronounced if the dogs was female or if it took part in agility copettions with is owner.
Previous research has found that cortisol in humans and their dogs can rise together in the short term especially when competing. But this finding was someting new. " This is the first time we've seen a long term synchroniation in stress levels between members of two diferent species。
We haven't scen this between humans and dogs before." lead research lina r oth told the guardian.And what about a pooch's lifestyle?did limited opportunitics for play or more time spent alone stress out the dogs? nearly as much as belonging to a human with high cortisol levels. The personality of the owner seemed to play a role to. Although that varied with the sex of the dog.
Female dogs whose owners had higher scores in the Big five traits of neurotic ism openness, and conscientiousness had higher cortisol levels, while the same was true of male dogs whose owners scored high in agreeableness.
This will not come as a huge surprise to many observant folks who have noticed that highly stung people offen have a highly strung dogs. But should scientifie confrmation of this conection between owners and their dogs put pet if you're arcciety prone? Or if you're under a lot of stress and already a pet owner, should you feel guilty?
Roth replies" 1 don't think you should be anxious that , if you're sressed,, you might harm your dog" instead, your dog is a 8ocial support for you, and you are a social support for the dog.
Your sressede out than made up for by exstra pats , belly rubs, and tennis ball throws.
Though if you do lean towards the anxious side, you might want to think carefully about choosing a resilient type of dog. Just which breeds are best is still an open question.one Roth andher collaborators hope.
It may be possible to match dog and owner in a way that is better for both, from a stress- management says" It may be that certain breeds are not so deeply afected if their owner hasa high sres leve!""
Which of the fllowing statement is not true? ()
A New Study Says You Can Spread to Your Dog
Research shows that most dog owner's find their pets to be great stress busters.Curling up on the couch with your pug on playing eatch with your Labradoodle is a great way to unwind and letthe cares of the dlay slip away . New science has some bud news for dog owners. Dog might ease your stress. but they can also catch it,
I's an old joke that dogs resemble their owners, but according to this new study out of linkoping universily in sweden . Its actually true in one lecus funny way: stressed out owners have stressedout dog .
To figure this out the researchers took hair samples from 25 border collies and 33 shetland sheepdogs. AS well as their female owners. For both humans and dogs . Hair records the level of the stress bormone cortisol in the body over time s0 by analy zing these hairs, the team could figure out just now much stress both the owners and their pets were under long_ ferm.
The studly found the stress level of the dogs and their owners matched up : higher levels of sitress among owners showed up as higher levels of stress in their dogs. The efct was even more pronounced if the dogs was female or if it took part in agility copettions with is owner.
Previous research has found that cortisol in humans and their dogs can rise together in the short term especially when competing. But this finding was someting new. " This is the first time we've seen a long term synchroniation in stress levels between members of two diferent species。
We haven't scen this between humans and dogs before." lead research lina r oth told the guardian.And what about a pooch's lifestyle?did limited opportunitics for play or more time spent alone stress out the dogs? nearly as much as belonging to a human with high cortisol levels. The personality of the owner seemed to play a role to. Although that varied with the sex of the dog.
Female dogs whose owners had higher scores in the Big five traits of neurotic ism openness, and conscientiousness had higher cortisol levels, while the same was true of male dogs whose owners scored high in agreeableness.
This will not come as a huge surprise to many observant folks who have noticed that highly stung people offen have a highly strung dogs. But should scientifie confrmation of this conection between owners and their dogs put pet if you're arcciety prone? Or if you're under a lot of stress and already a pet owner, should you feel guilty?
Roth replies" 1 don't think you should be anxious that , if you're sressed,, you might harm your dog" instead, your dog is a 8ocial support for you, and you are a social support for the dog.
Your sressede out than made up for by exstra pats , belly rubs, and tennis ball throws.
Though if you do lean towards the anxious side, you might want to think carefully about choosing a resilient type of dog. Just which breeds are best is still an open question.one Roth andher collaborators hope.
It may be possible to match dog and owner in a way that is better for both, from a stress- management says" It may be that certain breeds are not so deeply afected if their owner hasa high sres leve!""
What makes this study different from previous research which also saw oortisol synchronization in dogs?()
A New Study Says You Can Spread to Your Dog
Research shows that most dog owner's find their pets to be great stress busters.Curling up on the couch with your pug on playing eatch with your Labradoodle is a great way to unwind and letthe cares of the dlay slip away . New science has some bud news for dog owners. Dog might ease your stress. but they can also catch it,
I's an old joke that dogs resemble their owners, but according to this new study out of linkoping universily in sweden . Its actually true in one lecus funny way: stressed out owners have stressedout dog .
To figure this out the researchers took hair samples from 25 border collies and 33 shetland sheepdogs. AS well as their female owners. For both humans and dogs . Hair records the level of the stress bormone cortisol in the body over time s0 by analy zing these hairs, the team could figure out just now much stress both the owners and their pets were under long_ ferm.
The studly found the stress level of the dogs and their owners matched up : higher levels of sitress among owners showed up as higher levels of stress in their dogs. The efct was even more pronounced if the dogs was female or if it took part in agility copettions with is owner.
Previous research has found that cortisol in humans and their dogs can rise together in the short term especially when competing. But this finding was someting new. " This is the first time we've seen a long term synchroniation in stress levels between members of two diferent species。
We haven't scen this between humans and dogs before." lead research lina r oth told the guardian.And what about a pooch's lifestyle?did limited opportunitics for play or more time spent alone stress out the dogs? nearly as much as belonging to a human with high cortisol levels. The personality of the owner seemed to play a role to. Although that varied with the sex of the dog.
Female dogs whose owners had higher scores in the Big five traits of neurotic ism openness, and conscientiousness had higher cortisol levels, while the same was true of male dogs whose owners scored high in agreeableness.
This will not come as a huge surprise to many observant folks who have noticed that highly stung people offen have a highly strung dogs. But should scientifie confrmation of this conection between owners and their dogs put pet if you're arcciety prone? Or if you're under a lot of stress and already a pet owner, should you feel guilty?
Roth replies" 1 don't think you should be anxious that , if you're sressed,, you might harm your dog" instead, your dog is a 8ocial support for you, and you are a social support for the dog.
Your sressede out than made up for by exstra pats , belly rubs, and tennis ball throws.
Though if you do lean towards the anxious side, you might want to think carefully about choosing a resilient type of dog. Just which breeds are best is still an open question.one Roth andher collaborators hope.
It may be possible to match dog and owner in a way that is better for both, from a stress- management says" It may be that certain breeds are not so deeply afected if their owner hasa high sres leve!""
The auther writes the first para in order to ( )
A New Study Says You Can Spread to Your Dog
Research shows that most dog owner's find their pets to be great stress busters.Curling up on the couch with your pug on playing eatch with your Labradoodle is a great way to unwind and letthe cares of the dlay slip away . New science has some bud news for dog owners. Dog might ease your stress. but they can also catch it,
I's an old joke that dogs resemble their owners, but according to this new study out of linkoping universily in sweden . Its actually true in one lecus funny way: stressed out owners have stressedout dog .
To figure this out the researchers took hair samples from 25 border collies and 33 shetland sheepdogs. AS well as their female owners. For both humans and dogs . Hair records the level of the stress bormone cortisol in the body over time s0 by analy zing these hairs, the team could figure out just now much stress both the owners and their pets were under long_ ferm.
The studly found the stress level of the dogs and their owners matched up : higher levels of sitress among owners showed up as higher levels of stress in their dogs. The efct was even more pronounced if the dogs was female or if it took part in agility copettions with is owner.
Previous research has found that cortisol in humans and their dogs can rise together in the short term especially when competing. But this finding was someting new. " This is the first time we've seen a long term synchroniation in stress levels between members of two diferent species。
We haven't scen this between humans and dogs before." lead research lina r oth told the guardian.And what about a pooch's lifestyle?did limited opportunitics for play or more time spent alone stress out the dogs? nearly as much as belonging to a human with high cortisol levels. The personality of the owner seemed to play a role to. Although that varied with the sex of the dog.
Female dogs whose owners had higher scores in the Big five traits of neurotic ism openness, and conscientiousness had higher cortisol levels, while the same was true of male dogs whose owners scored high in agreeableness.
This will not come as a huge surprise to many observant folks who have noticed that highly stung people offen have a highly strung dogs. But should scientifie confrmation of this conection between owners and their dogs put pet if you're arcciety prone? Or if you're under a lot of stress and already a pet owner, should you feel guilty?
Roth replies" 1 don't think you should be anxious that , if you're sressed,, you might harm your dog" instead, your dog is a 8ocial support for you, and you are a social support for the dog.
Your sressede out than made up for by exstra pats , belly rubs, and tennis ball throws.
Though if you do lean towards the anxious side, you might want to think carefully about choosing a resilient type of dog. Just which breeds are best is still an open question.one Roth andher collaborators hope.
It may be possible to match dog and owner in a way that is better for both, from a stress- management says" It may be that certain breeds are not so deeply afected if their owner hasa high sres leve!""
Which factor canmot result in dog's stess?()
黑颈鹤和斑头雁每年都要迁徙到青海湖进行繁殖。青海湖地处青海高原东北部的青海湖盆地内，位于西宁市西北部100公里外，是中国第一大内陆湖泊。黑颈鹤在云贵等地过冬，到了春天就一路向北飞行3000公里来这里.而斑头雁冬天的活动范围则更往南，远到印度，因此，它们所面临的旅程也更加艰难:一方面是路途遥远，另一方面斑头雁冬天的栖息地与海平面齐平，夏天的繁殖地的海拔则高达3000米，横亘其间的是高大的喜马拉雅山脉。它们至少要飞行到海拔5000米的高度才能逾越这道令人望而生畏的屏障。通过飞行爬升到如此高度并非易事，在这个海拔高度，空气的密度大概只有海平面的一半，因此鸟儿通过振动翅膀产生升力就要消耗更多能量。另外，氧的分压也同样会降低，这也会阻碍它们获得足够的氧气来补给飞行过程的消耗.，直到几年前，鸟类如何实现这一壮举的动力学机制还是个谜， 但2011年美国科学院院刊(PNAS) 一篇里程碑式的文章为我们揭示了它们是如何做到这一点的。文章作者用全球定位系统(GPS)跟踪这些迁徙的鸟儿，发现它们通常一天之内就可以飞越喜马拉雅山。在6~7个小时内就从海平面高度的出发点-最作气飞到海拔6000米。最令人惊讶的是，白天会有南风吹上山脊，这些鸟儿本可以充分借助这些风来减小能量消耗，然而，班头雁并不这么做:相反，它们等到相对平静的夜晚，完全靠白己的体力来完成这一飞越。斑头雁和恩颈鹤在飞行中有-个共同特点,就是它们经常是以某种队形来飞行的。队形
多种多样，但通常是后面的鸟儿飞在前一只鸟的侧后方,因此就有了常见的“人”字形队形。几十年来，关于鸟儿为什么以这样的队形来迁飞有许多猜测，有两种观点比较流行。
第一种观点认为，人字队形与定向有关。以斑头雁飞越喜马拉雅山为例，该行程需要找到和穿越几个高海拔的通道，利用这些通道也许能节省几千米的上升高度。斑头雁的寿命有20~-30年，有些个体已经从印度向北迁飞了许多次。因此，很可能是年长有经验的斑头雁
在队伍的前面带路，取道最经济的路线，而无需飞越最高的山峰(这也偶有发生，比如有小群鸟儿飞越珠穆朗玛峰的情形)。这一观点带来了几个难以回答的问题:为什么鸟儿要保持人字形队列，而不是一只紧跟一只?另外，保持队形似乎只是黑颈鹤、斑头雁这样体型较大
的鸟类的特征。许多小型的候鸟成群迁飞时，通常是处于混乱的模式。虽然它们也有定向的需求，但没有排成人字形也没有问题。
第二种观点认为，这种按一定队形迁飞的行为与节约能量以降低迁徙飞行的能量消耗有关。在最近冬奥会上的速滑项目和夏季奥运会的白行车项目中也你会看到类似的行为。在比宴中，速滑或自行车运动员以一种很紧凑的队形前进，-名运动员在前，另外三名依次紧随
其后。速滑和自行车比赛中，很重要的一部分体能消耗是为了克服空气阻力。后面的三名选手都能受益，因为这种队形能减少他们所受到的空气阻力，但前面开路的选手由于需要克服全部阻力很容易精疲力尽。因此，在速滑和自行车比赛中，参赛选手会轮流在前面开路，从
而保证大家都能同等受益。对以人字形队列迁徙的鸟进行仔细观察发现，它们也是采用这种团队协作的方式，前面带路的鸟儿不时与后面的鸟儿换位。那么，如果以队形的形式迁飞是为了减小空气阻力，为什么鸟儿不选择以直线的队形来飞行2因为一个紧跟一个飞行似乎能
最大程度地减小眼随者需要克服的空气阻力。毫无疑问，速滑或自行车团队如果采用人字队形是不可能拿到冠军的。飞行运动与陆地上的运动一个关键的不同点是，飞行运动除了要克服水平方向.上的空气阻力,还需要产生保持飞行状态的上升力。自行车运动员和速滑运动员
没有这个问题，因为他们有地面反作用力的支撑。也许，飞行时 稍微偏移位于前面的同伴，并不能在最大程度上减少空气阻力,但能够在某种程度上减少跟随的鸟儿保持升力的体能消耗。
事实上,我们有足够的理由相信这一推断， 飞行中的鸟的翅膀会形成一股涡旋状的循环气流。当你从鸟儿的背后来观察时就会发现这个循环气流，来自右边翅膀的涡流逆时针旋转，而来自左边翅膀的涡流则顺时针旋转，那么在正中间，即鸟儿正后方尾随的两股涡流中，气
流都是向下的，而两侧的气流都是向上的。这样一来，鸟儿没有选择紧跟在同伴的正后方飞行的原因就显而易见了。如果鸟儿飞在同伴的正后方，那么它将处于向下的气流中，这额外增加了它们维持飞行状态的能耗。相反，当位于同伴的后侧方时，它们可以利用这一向上的
气流,得到升力。这确实有效。有人曾经驾驶轻型飞机并保持相互之间稍微偏移，他们发现，当尾随的飞机处于前面飞机机翼涡流的向上气流中时，消耗的燃料显著低于前面的飞机。以这种方式节约的燃料能够多达18%，这个效应广“泛应用在军用飞机中以降低油耗。然而这对于大型客机并不适用，因为要达到节油效果，飞机需要足够靠近，这会增加安全风险。
从文中可知，斑头雁呈人字飞行时，一只总是在另一只侧后方的原因是( ).
黑颈鹤和斑头雁每年都要迁徙到青海湖进行繁殖。青海湖地处青海高原东北部的青海湖盆地内，位于西宁市西北部100公里外，是中国第一大内陆湖泊。黑颈鹤在云贵等地过冬，到了春天就一路向北飞行3000公里来这里.而斑头雁冬天的活动范围则更往南，远到印度，因此，它们所面临的旅程也更加艰难:一方面是路途遥远，另一方面斑头雁冬天的栖息地与海平面齐平，夏天的繁殖地的海拔则高达3000米，横亘其间的是高大的喜马拉雅山脉。它们至少要飞行到海拔5000米的高度才能逾越这道令人望而生畏的屏障。通过飞行爬升到如此高度并非易事，在这个海拔高度，空气的密度大概只有海平面的一半，因此鸟儿通过振动翅膀产生升力就要消耗更多能量。另外，氧的分压也同样会降低，这也会阻碍它们获得足够的氧气来补给飞行过程的消耗.，直到几年前，鸟类如何实现这一壮举的动力学机制还是个谜， 但2011年美国科学院院刊(PNAS) 一篇里程碑式的文章为我们揭示了它们是如何做到这一点的。文章作者用全球定位系统(GPS)跟踪这些迁徙的鸟儿，发现它们通常一天之内就可以飞越喜马拉雅山。在6~7个小时内就从海平面高度的出发点-最作气飞到海拔6000米。最令人惊讶的是，白天会有南风吹上山脊，这些鸟儿本可以充分借助这些风来减小能量消耗，然而，班头雁并不这么做:相反，它们等到相对平静的夜晚，完全靠白己的体力来完成这一飞越。斑头雁和恩颈鹤在飞行中有-个共同特点,就是它们经常是以某种队形来飞行的。队形
多种多样，但通常是后面的鸟儿飞在前一只鸟的侧后方,因此就有了常见的“人”字形队形。几十年来，关于鸟儿为什么以这样的队形来迁飞有许多猜测，有两种观点比较流行。
第一种观点认为，人字队形与定向有关。以斑头雁飞越喜马拉雅山为例，该行程需要找到和穿越几个高海拔的通道，利用这些通道也许能节省几千米的上升高度。斑头雁的寿命有20~-30年，有些个体已经从印度向北迁飞了许多次。因此，很可能是年长有经验的斑头雁
在队伍的前面带路，取道最经济的路线，而无需飞越最高的山峰(这也偶有发生，比如有小群鸟儿飞越珠穆朗玛峰的情形)。这一观点带来了几个难以回答的问题:为什么鸟儿要保持人字形队列，而不是一只紧跟一只?另外，保持队形似乎只是黑颈鹤、斑头雁这样体型较大
的鸟类的特征。许多小型的候鸟成群迁飞时，通常是处于混乱的模式。虽然它们也有定向的需求，但没有排成人字形也没有问题。
第二种观点认为，这种按一定队形迁飞的行为与节约能量以降低迁徙飞行的能量消耗有关。在最近冬奥会上的速滑项目和夏季奥运会的白行车项目中也你会看到类似的行为。在比宴中，速滑或自行车运动员以一种很紧凑的队形前进，-名运动员在前，另外三名依次紧随
其后。速滑和自行车比赛中，很重要的一部分体能消耗是为了克服空气阻力。后面的三名选手都能受益，因为这种队形能减少他们所受到的空气阻力，但前面开路的选手由于需要克服全部阻力很容易精疲力尽。因此，在速滑和自行车比赛中，参赛选手会轮流在前面开路，从
而保证大家都能同等受益。对以人字形队列迁徙的鸟进行仔细观察发现，它们也是采用这种团队协作的方式，前面带路的鸟儿不时与后面的鸟儿换位。那么，如果以队形的形式迁飞是为了减小空气阻力，为什么鸟儿不选择以直线的队形来飞行2因为一个紧跟一个飞行似乎能
最大程度地减小眼随者需要克服的空气阻力。毫无疑问，速滑或自行车团队如果采用人字队形是不可能拿到冠军的。飞行运动与陆地上的运动一个关键的不同点是，飞行运动除了要克服水平方向.上的空气阻力,还需要产生保持飞行状态的上升力。自行车运动员和速滑运动员
没有这个问题，因为他们有地面反作用力的支撑。也许，飞行时 稍微偏移位于前面的同伴，并不能在最大程度上减少空气阻力,但能够在某种程度上减少跟随的鸟儿保持升力的体能消耗。
事实上,我们有足够的理由相信这一推断， 飞行中的鸟的翅膀会形成一股涡旋状的循环气流。当你从鸟儿的背后来观察时就会发现这个循环气流，来自右边翅膀的涡流逆时针旋转，而来自左边翅膀的涡流则顺时针旋转，那么在正中间，即鸟儿正后方尾随的两股涡流中，气
流都是向下的，而两侧的气流都是向上的。这样一来，鸟儿没有选择紧跟在同伴的正后方飞行的原因就显而易见了。如果鸟儿飞在同伴的正后方，那么它将处于向下的气流中，这额外增加了它们维持飞行状态的能耗。相反，当位于同伴的后侧方时，它们可以利用这一向上的
气流,得到升力。这确实有效。有人曾经驾驶轻型飞机并保持相互之间稍微偏移，他们发现，当尾随的飞机处于前面飞机机翼涡流的向上气流中时，消耗的燃料显著低于前面的飞机。以这种方式节约的燃料能够多达18%，这个效应广“泛应用在军用飞机中以降低油耗。然而这对于大型客机并不适用，因为要达到节油效果，飞机需要足够靠近，这会增加安全风险。
文中举了遠滑项目和自行车项目是为了说明( )。
黑颈鹤和斑头雁每年都要迁徙到青海湖进行繁殖。青海湖地处青海高原东北部的青海湖盆地内，位于西宁市西北部100公里外，是中国第一大内陆湖泊。黑颈鹤在云贵等地过冬，到了春天就一路向北飞行3000公里来这里.而斑头雁冬天的活动范围则更往南，远到印度，因此，它们所面临的旅程也更加艰难:一方面是路途遥远，另一方面斑头雁冬天的栖息地与海平面齐平，夏天的繁殖地的海拔则高达3000米，横亘其间的是高大的喜马拉雅山脉。它们至少要飞行到海拔5000米的高度才能逾越这道令人望而生畏的屏障。通过飞行爬升到如此高度并非易事，在这个海拔高度，空气的密度大概只有海平面的一半，因此鸟儿通过振动翅膀产生升力就要消耗更多能量。另外，氧的分压也同样会降低，这也会阻碍它们获得足够的氧气来补给飞行过程的消耗.，直到几年前，鸟类如何实现这一壮举的动力学机制还是个谜， 但2011年美国科学院院刊(PNAS) 一篇里程碑式的文章为我们揭示了它们是如何做到这一点的。文章作者用全球定位系统(GPS)跟踪这些迁徙的鸟儿，发现它们通常一天之内就可以飞越喜马拉雅山。在6~7个小时内就从海平面高度的出发点-最作气飞到海拔6000米。最令人惊讶的是，白天会有南风吹上山脊，这些鸟儿本可以充分借助这些风来减小能量消耗，然而，班头雁并不这么做:相反，它们等到相对平静的夜晚，完全靠白己的体力来完成这一飞越。斑头雁和恩颈鹤在飞行中有-个共同特点,就是它们经常是以某种队形来飞行的。队形
多种多样，但通常是后面的鸟儿飞在前一只鸟的侧后方,因此就有了常见的“人”字形队形。几十年来，关于鸟儿为什么以这样的队形来迁飞有许多猜测，有两种观点比较流行。
第一种观点认为，人字队形与定向有关。以斑头雁飞越喜马拉雅山为例，该行程需要找到和穿越几个高海拔的通道，利用这些通道也许能节省几千米的上升高度。斑头雁的寿命有20~-30年，有些个体已经从印度向北迁飞了许多次。因此，很可能是年长有经验的斑头雁
在队伍的前面带路，取道最经济的路线，而无需飞越最高的山峰(这也偶有发生，比如有小群鸟儿飞越珠穆朗玛峰的情形)。这一观点带来了几个难以回答的问题:为什么鸟儿要保持人字形队列，而不是一只紧跟一只?另外，保持队形似乎只是黑颈鹤、斑头雁这样体型较大
的鸟类的特征。许多小型的候鸟成群迁飞时，通常是处于混乱的模式。虽然它们也有定向的需求，但没有排成人字形也没有问题。
第二种观点认为，这种按一定队形迁飞的行为与节约能量以降低迁徙飞行的能量消耗有关。在最近冬奥会上的速滑项目和夏季奥运会的白行车项目中也你会看到类似的行为。在比宴中，速滑或自行车运动员以一种很紧凑的队形前进，-名运动员在前，另外三名依次紧随
其后。速滑和自行车比赛中，很重要的一部分体能消耗是为了克服空气阻力。后面的三名选手都能受益，因为这种队形能减少他们所受到的空气阻力，但前面开路的选手由于需要克服全部阻力很容易精疲力尽。因此，在速滑和自行车比赛中，参赛选手会轮流在前面开路，从
而保证大家都能同等受益。对以人字形队列迁徙的鸟进行仔细观察发现，它们也是采用这种团队协作的方式，前面带路的鸟儿不时与后面的鸟儿换位。那么，如果以队形的形式迁飞是为了减小空气阻力，为什么鸟儿不选择以直线的队形来飞行2因为一个紧跟一个飞行似乎能
最大程度地减小眼随者需要克服的空气阻力。毫无疑问，速滑或自行车团队如果采用人字队形是不可能拿到冠军的。飞行运动与陆地上的运动一个关键的不同点是，飞行运动除了要克服水平方向.上的空气阻力,还需要产生保持飞行状态的上升力。自行车运动员和速滑运动员
没有这个问题，因为他们有地面反作用力的支撑。也许，飞行时 稍微偏移位于前面的同伴，并不能在最大程度上减少空气阻力,但能够在某种程度上减少跟随的鸟儿保持升力的体能消耗。
事实上,我们有足够的理由相信这一推断， 飞行中的鸟的翅膀会形成一股涡旋状的循环气流。当你从鸟儿的背后来观察时就会发现这个循环气流，来自右边翅膀的涡流逆时针旋转，而来自左边翅膀的涡流则顺时针旋转，那么在正中间，即鸟儿正后方尾随的两股涡流中，气
流都是向下的，而两侧的气流都是向上的。这样一来，鸟儿没有选择紧跟在同伴的正后方飞行的原因就显而易见了。如果鸟儿飞在同伴的正后方，那么它将处于向下的气流中，这额外增加了它们维持飞行状态的能耗。相反，当位于同伴的后侧方时，它们可以利用这一向上的
气流,得到升力。这确实有效。有人曾经驾驶轻型飞机并保持相互之间稍微偏移，他们发现，当尾随的飞机处于前面飞机机翼涡流的向上气流中时，消耗的燃料显著低于前面的飞机。以这种方式节约的燃料能够多达18%，这个效应广“泛应用在军用飞机中以降低油耗。然而这对于大型客机并不适用，因为要达到节油效果，飞机需要足够靠近，这会增加安全风险。
下列论据中，最能削弱文中“人字形与定向有关”这个观点的是0
黑颈鹤和斑头雁每年都要迁徙到青海湖进行繁殖。青海湖地处青海高原东北部的青海湖盆地内，位于西宁市西北部100公里外，是中国第一大内陆湖泊。黑颈鹤在云贵等地过冬，到了春天就一路向北飞行3000公里来这里.而斑头雁冬天的活动范围则更往南，远到印度，因此，它们所面临的旅程也更加艰难:一方面是路途遥远，另一方面斑头雁冬天的栖息地与海平面齐平，夏天的繁殖地的海拔则高达3000米，横亘其间的是高大的喜马拉雅山脉。它们至少要飞行到海拔5000米的高度才能逾越这道令人望而生畏的屏障。通过飞行爬升到如此高度并非易事，在这个海拔高度，空气的密度大概只有海平面的一半，因此鸟儿通过振动翅膀产生升力就要消耗更多能量。另外，氧的分压也同样会降低，这也会阻碍它们获得足够的氧气来补给飞行过程的消耗.，直到几年前，鸟类如何实现这一壮举的动力学机制还是个谜， 但2011年美国科学院院刊(PNAS) 一篇里程碑式的文章为我们揭示了它们是如何做到这一点的。文章作者用全球定位系统(GPS)跟踪这些迁徙的鸟儿，发现它们通常一天之内就可以飞越喜马拉雅山。在6~7个小时内就从海平面高度的出发点-最作气飞到海拔6000米。最令人惊讶的是，白天会有南风吹上山脊，这些鸟儿本可以充分借助这些风来减小能量消耗，然而，班头雁并不这么做:相反，它们等到相对平静的夜晚，完全靠白己的体力来完成这一飞越。斑头雁和恩颈鹤在飞行中有-个共同特点,就是它们经常是以某种队形来飞行的。队形
多种多样，但通常是后面的鸟儿飞在前一只鸟的侧后方,因此就有了常见的“人”字形队形。几十年来，关于鸟儿为什么以这样的队形来迁飞有许多猜测，有两种观点比较流行。
第一种观点认为，人字队形与定向有关。以斑头雁飞越喜马拉雅山为例，该行程需要找到和穿越几个高海拔的通道，利用这些通道也许能节省几千米的上升高度。斑头雁的寿命有20~-30年，有些个体已经从印度向北迁飞了许多次。因此，很可能是年长有经验的斑头雁
在队伍的前面带路，取道最经济的路线，而无需飞越最高的山峰(这也偶有发生，比如有小群鸟儿飞越珠穆朗玛峰的情形)。这一观点带来了几个难以回答的问题:为什么鸟儿要保持人字形队列，而不是一只紧跟一只?另外，保持队形似乎只是黑颈鹤、斑头雁这样体型较大
的鸟类的特征。许多小型的候鸟成群迁飞时，通常是处于混乱的模式。虽然它们也有定向的需求，但没有排成人字形也没有问题。
第二种观点认为，这种按一定队形迁飞的行为与节约能量以降低迁徙飞行的能量消耗有关。在最近冬奥会上的速滑项目和夏季奥运会的白行车项目中也你会看到类似的行为。在比宴中，速滑或自行车运动员以一种很紧凑的队形前进，-名运动员在前，另外三名依次紧随
其后。速滑和自行车比赛中，很重要的一部分体能消耗是为了克服空气阻力。后面的三名选手都能受益，因为这种队形能减少他们所受到的空气阻力，但前面开路的选手由于需要克服全部阻力很容易精疲力尽。因此，在速滑和自行车比赛中，参赛选手会轮流在前面开路，从
而保证大家都能同等受益。对以人字形队列迁徙的鸟进行仔细观察发现，它们也是采用这种团队协作的方式，前面带路的鸟儿不时与后面的鸟儿换位。那么，如果以队形的形式迁飞是为了减小空气阻力，为什么鸟儿不选择以直线的队形来飞行2因为一个紧跟一个飞行似乎能
最大程度地减小眼随者需要克服的空气阻力。毫无疑问，速滑或自行车团队如果采用人字队形是不可能拿到冠军的。飞行运动与陆地上的运动一个关键的不同点是，飞行运动除了要克服水平方向.上的空气阻力,还需要产生保持飞行状态的上升力。自行车运动员和速滑运动员
没有这个问题，因为他们有地面反作用力的支撑。也许，飞行时 稍微偏移位于前面的同伴，并不能在最大程度上减少空气阻力,但能够在某种程度上减少跟随的鸟儿保持升力的体能消耗。
事实上,我们有足够的理由相信这一推断， 飞行中的鸟的翅膀会形成一股涡旋状的循环气流。当你从鸟儿的背后来观察时就会发现这个循环气流，来自右边翅膀的涡流逆时针旋转，而来自左边翅膀的涡流则顺时针旋转，那么在正中间，即鸟儿正后方尾随的两股涡流中，气
流都是向下的，而两侧的气流都是向上的。这样一来，鸟儿没有选择紧跟在同伴的正后方飞行的原因就显而易见了。如果鸟儿飞在同伴的正后方，那么它将处于向下的气流中，这额外增加了它们维持飞行状态的能耗。相反，当位于同伴的后侧方时，它们可以利用这一向上的
气流,得到升力。这确实有效。有人曾经驾驶轻型飞机并保持相互之间稍微偏移，他们发现，当尾随的飞机处于前面飞机机翼涡流的向上气流中时，消耗的燃料显著低于前面的飞机。以这种方式节约的燃料能够多达18%，这个效应广“泛应用在军用飞机中以降低油耗。然而这对于大型客机并不适用，因为要达到节油效果，飞机需要足够靠近，这会增加安全风险。
关于斑头雁迁徙的情形描述正确的个数是( )。
(1)青海湖足斑头雁的繁殖地，这里海拔大约3000米
(2)北半球冬季时，在喜马拉雅山脉或可看到斑头雁的踪影
(3)斑头雁一般选择气流平静的夜晚飞跃喜马拉雅山
(4)跟黑颈鵝- -样，斑头雁在迁徒中也会使用人字队形飞行
黑颈鹤和斑头雁每年都要迁徙到青海湖进行繁殖。青海湖地处青海高原东北部的青海湖盆地内，位于西宁市西北部100公里外，是中国第一大内陆湖泊。黑颈鹤在云贵等地过冬，到了春天就一路向北飞行3000公里来这里.而斑头雁冬天的活动范围则更往南，远到印度，因此，它们所面临的旅程也更加艰难:一方面是路途遥远，另一方面斑头雁冬天的栖息地与海平面齐平，夏天的繁殖地的海拔则高达3000米，横亘其间的是高大的喜马拉雅山脉。它们至少要飞行到海拔5000米的高度才能逾越这道令人望而生畏的屏障。通过飞行爬升到如此高度并非易事，在这个海拔高度，空气的密度大概只有海平面的一半，因此鸟儿通过振动翅膀产生升力就要消耗更多能量。另外，氧的分压也同样会降低，这也会阻碍它们获得足够的氧气来补给飞行过程的消耗.，直到几年前，鸟类如何实现这一壮举的动力学机制还是个谜， 但2011年美国科学院院刊(PNAS) 一篇里程碑式的文章为我们揭示了它们是如何做到这一点的。文章作者用全球定位系统(GPS)跟踪这些迁徙的鸟儿，发现它们通常一天之内就可以飞越喜马拉雅山。在6~7个小时内就从海平面高度的出发点-最作气飞到海拔6000米。最令人惊讶的是，白天会有南风吹上山脊，这些鸟儿本可以充分借助这些风来减小能量消耗，然而，班头雁并不这么做:相反，它们等到相对平静的夜晚，完全靠白己的体力来完成这一飞越。斑头雁和恩颈鹤在飞行中有-个共同特点,就是它们经常是以某种队形来飞行的。队形
多种多样，但通常是后面的鸟儿飞在前一只鸟的侧后方,因此就有了常见的“人”字形队形。几十年来，关于鸟儿为什么以这样的队形来迁飞有许多猜测，有两种观点比较流行。
第一种观点认为，人字队形与定向有关。以斑头雁飞越喜马拉雅山为例，该行程需要找到和穿越几个高海拔的通道，利用这些通道也许能节省几千米的上升高度。斑头雁的寿命有20~-30年，有些个体已经从印度向北迁飞了许多次。因此，很可能是年长有经验的斑头雁
在队伍的前面带路，取道最经济的路线，而无需飞越最高的山峰(这也偶有发生，比如有小群鸟儿飞越珠穆朗玛峰的情形)。这一观点带来了几个难以回答的问题:为什么鸟儿要保持人字形队列，而不是一只紧跟一只?另外，保持队形似乎只是黑颈鹤、斑头雁这样体型较大
的鸟类的特征。许多小型的候鸟成群迁飞时，通常是处于混乱的模式。虽然它们也有定向的需求，但没有排成人字形也没有问题。
第二种观点认为，这种按一定队形迁飞的行为与节约能量以降低迁徙飞行的能量消耗有关。在最近冬奥会上的速滑项目和夏季奥运会的白行车项目中也你会看到类似的行为。在比宴中，速滑或自行车运动员以一种很紧凑的队形前进，-名运动员在前，另外三名依次紧随
其后。速滑和自行车比赛中，很重要的一部分体能消耗是为了克服空气阻力。后面的三名选手都能受益，因为这种队形能减少他们所受到的空气阻力，但前面开路的选手由于需要克服全部阻力很容易精疲力尽。因此，在速滑和自行车比赛中，参赛选手会轮流在前面开路，从
而保证大家都能同等受益。对以人字形队列迁徙的鸟进行仔细观察发现，它们也是采用这种团队协作的方式，前面带路的鸟儿不时与后面的鸟儿换位。那么，如果以队形的形式迁飞是为了减小空气阻力，为什么鸟儿不选择以直线的队形来飞行2因为一个紧跟一个飞行似乎能
最大程度地减小眼随者需要克服的空气阻力。毫无疑问，速滑或自行车团队如果采用人字队形是不可能拿到冠军的。飞行运动与陆地上的运动一个关键的不同点是，飞行运动除了要克服水平方向.上的空气阻力,还需要产生保持飞行状态的上升力。自行车运动员和速滑运动员
没有这个问题，因为他们有地面反作用力的支撑。也许，飞行时 稍微偏移位于前面的同伴，并不能在最大程度上减少空气阻力,但能够在某种程度上减少跟随的鸟儿保持升力的体能消耗。
事实上,我们有足够的理由相信这一推断， 飞行中的鸟的翅膀会形成一股涡旋状的循环气流。当你从鸟儿的背后来观察时就会发现这个循环气流，来自右边翅膀的涡流逆时针旋转，而来自左边翅膀的涡流则顺时针旋转，那么在正中间，即鸟儿正后方尾随的两股涡流中，气
流都是向下的，而两侧的气流都是向上的。这样一来，鸟儿没有选择紧跟在同伴的正后方飞行的原因就显而易见了。如果鸟儿飞在同伴的正后方，那么它将处于向下的气流中，这额外增加了它们维持飞行状态的能耗。相反，当位于同伴的后侧方时，它们可以利用这一向上的
气流,得到升力。这确实有效。有人曾经驾驶轻型飞机并保持相互之间稍微偏移，他们发现，当尾随的飞机处于前面飞机机翼涡流的向上气流中时，消耗的燃料显著低于前面的飞机。以这种方式节约的燃料能够多达18%，这个效应广“泛应用在军用飞机中以降低油耗。然而这对于大型客机并不适用，因为要达到节油效果，飞机需要足够靠近，这会增加安全风险。
与恩颈鹅相比，班头雁迁德过程中面临的困难最主要的是( )。
