通读下面的短文，掌握其大意。然后，从每小题的四个选项中选出可填入相应空白处的最佳选项。
Living one's life is really like driving on a highway. First, to drive well, the driver must carefully examine the 21 of his car, just as he cares for his own health. Once, he goes on the highway, he must 22 certain rules for his own safety. Just as he must obey certain rules of society in order to be a decent（体面的）human being. For example, on the highway, he is 23 to keep a constant speed which can be compared with his 24 life. Neither driving nor living must be taken at too 25 a speed nor at too slow a speed. If he drives over 26 , the police will give him a ticket, just as he will be arrested when he breaks the law. Acting too conservatively（保守地）, he will be called old-fashioned 27 others as they drive at the proper speed. When he wants to change lanes, he must pay 28 to what he is doing and check in every direction. It is sometimes dangerous to change our way of life 29 one can be sure of success. He 30 not make any unnecessary changing of lanes which may be dangerous. Finally, he must discover where he is now by recognizing some 31 appearing now and then. If he takes the wrong way, he must return to the right, as 32 as he can. But he may thus lose 33 and energy both on the road and in life. On the whole, driving on a highway and living one's life are both hard work, 34 if he is careful and serious enough, 35 will provide him much pleasure.
____.
本题考查根据上下文选择合适的名词。该句要表达的意思是：开车前首先检查车的“状况”，正如人们关心自己的健康一样。其他选项都只是检查车况的某一个方面，表意太狭隘。A车轮，C引擎盖，D安全带，因此本题选择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_______。
