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最佳选项。
Many people go to school for an edueation. 21 learn languages, history, geography, physics, chemistry and maths. Others go to school to learn a skill so that they can 22 a living. School 23 is very important and useful. Yet no one can learn everything from school. A teacher, no matter how much he 24 , can not teach his students everything they 25 to know. The teacher's job is to show his students how to read and how to 26 . So much more is to be learned 27 school by the students themselves.
It is always more important to know how to study by 28 than to memorize（熟记）some facts or formula（公式）. It is 29 quite easy to learn a 30 fact in history or a formula in mathematics. But it is very difficult to use a formula in 31 out a maths problem. Great scientists, such as Einstein, Newton and Galileo, didn't learn many things from school. But they were all so 32 that they invented so many things for mankind.
The 33 for their success is that they knew how to study. They read books that were not 34 at school. They worked hard all their lives, wasting not a single moment. They would ask many questions as they read and they did thousands of 35 .
____.
make a living意思是“谋生”，这里表示学一门技术来谋生。
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_______。
