根据下面资料，回答36-39题
Some farmers in California are having a hard time picking their crops．There are not enough workers to help them with the harvest．
One farmer used to grow peaches (桃子), but will soon grow almonds (杏仁) instead．Peaches require more labor to harvest．They are easy to be damaged and need careful hand picking．He is now removing his peach trees．Then he will plant almond trees in their places． Almonds are harvested differently．It does not take as many workers to pick them because a machine shakes the almond trees．
The nuts fall on the ground and then are gathered up．The farmer does not have to hire many workers．
Some farmers think there are two reasons why they can' t find enough farm workers．One reason is that there are a lot of well-paid construction jobs in the are
A．Many people are taking these jobs instead of picking fruit．The other reason is that it has become more difficult for workers to come from Mexico into
California．Fewer workers are allowed to get into the country to work on the fruit farms．To settle the problem, farmers hope the government might allow these workers to work as guests．That would help workers provide for their family and help farmers harvest their crops．When the harvest season is over they' ll go back home．Farmers say that unless things change, more fruits will come from other countries．
This is because labor is cheaper in those countries than in the United States．
Why can' t some farmers find enough workers to pick fruit
事实细节题。根据第三段前三句可知，一些农场主认为他们找不到足够的农场工人有两个原因，一个是当地有许多高薪的建筑工作，很多人愿意从事这类工作而不愿意采摘水果。故本题选B。
把10gMgCl2和MgSO4的混合物溶于适量水中，滴加2mol／L的BaCl2溶液至沉淀完全，共消耗BaCl2溶液25mL。求混合物中MgCl2和MgSO4的质量各是多少克
固定在匀强磁场中的正方形导线框abcd，各边长为1．其中ab是一段电阻为R的均匀电阻丝，其余3边均为电阻可忽略的铜线。磁场的磁感应强度为B，方向垂直纸面向里。现有一与ab段的材料、粗细、长度都相同的电阻丝PQ架在导体框上，如图所示。PQ以恒定速度方向如何
一小物块以速度v0=10m／s沿光滑地面滑行，然后沿光滑曲面上升到顶部水平的高台上，并由高台上飞出，如图所示。问当高台的高度h多大时，小物块飞行的水平距离最大这个距离是多少(g=10m／s2)
某晶体盐的水溶液呈浅绿色，在此溶液中通入氯气，溶液变为棕黄色，把所得棕黄色溶液分成两份：一份加入KSCN溶液，溶液变深红色；另一份加入BaCl2溶液，产生不溶于稀HNO3的白色沉淀，则该晶体盐的化学式是_______。
欲除去乙烷中的乙烯，可将混合气体通过盛有_______的洗气瓶；欲除去乙炔中的硫化氢，可将混合气体通过盛有_______的洗气瓶。
浓硝酸常盛装在棕色瓶中，且贮放在冷暗处，原因是_______，
碳酸氢钠溶液和烧碱溶液反应的离子方程式为_______。
常温下，氨水中存在的离子有_______。
在酸或碱存在的条件下，甲酸甲酯跟水发生水解反应的化学方程式为_______。
有下列几种气体：H2、O2、HCl、NO、NH3、CH4，其中通常情况下能用来和水做“喷泉”实验的是_______。
