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。
A thousand years ago, Hong Kong was covered by a thick forest. As more and more people came to 21 in Hong Kong, these trees were cut down and burnt. Now there is 22 forest left, though there are still some small areas covered with trees. We call these woods.
Elephants, tigers and many 23 animals were living in the thick forest. When people came to live in Hong Kong, the 24 began to die out. Early farmers grew rice and 25 pigs and chickens in the valleys. They cut down the trees and burnt them. They needed 26 to keep themselves warm in winter, to cook their food and to keep away the dangerous animals. Elephants quickly disappeared because there was not enough food for them. 27 did most of the wolves and tigers. Monkeys and many other animals soon 28 in the same way.
You might think that there are no longer any animals in Hong Kong 29 in the zoos. There are still about 36 different animals 30 there. One of the most interesting of Hong Kong’s animals is the barking deer. These are beautiful little animals 31 a rich brown coat and a white patch under the tail. They look like deer 32 but they are much like a dog 33 . In Hong Kong the barking deer has only a real enemy－34 . People hunt these little animals though it is illegal. There are now not many barking deer left. So it is important 35 people to protect wild animals.
____.
many other animals表示其余的许多种动物，但不代表世界上所有的动物，故不选the other。
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_______。
