问题
填空题
甲、乙两数的积是x，甲数是12，乙数是______．
答案
乙数是x÷2．
故答案为：x÷2．
搜题请搜索小程序“爱下问搜题”
甲、乙两数的积是x，甲数是12，乙数是______．
乙数是x÷2．
故答案为：x÷2．
A thousand years ago Hong Kong was covered by a thick forest. As more and more people came to 1 in Hong Kong, these trees were cut down and burnt. Now there is 2 forest left, though there are still some small areas covered in trees．We call these woods. Elephants, tigers and many 3 animals were living in the thick forest. When people came to live in Hong Kong, the 4 began to die out. Early farmers grew rice and 5 pigs and chickens in the valleys. They cut down the trees and burnt them. They needed 6 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. 7 did most of the wolves and tigers. Monkeys and many other animals soon 8 in the same way. You might think that there are no longer any animals in Hong Kong 9 in the zoos. But there are still about 36 different animals 10 there. One of the most interesting of Hong Kong's animals is the barking deer.
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探究“蟾蜍的学习行为”
提出问题：蟾蜍是否具有学习行为？
作出假设：______？
制定并实施计划；
材料用具：蟾蜍，小蝗虫（若干），大野蜂（若干），细线等．方法步骤；
（1）用线吊着一只小蝗虫在蟾蜍眼前晃动，逗引一只饥饿的蟾蜍，观察蟾蜍的反应．
（2）用线吊着一只大野蜂在蟾蜍眼前晃动，逗引这只蟾蜍，观察蟾蜍的反应．
（3）用线吊着另一只大野蜂在蟾蜍眼前晃动，逗引这只蟾蜍，观察蟾蜍的反应．
（4）最后，还用线吊着另一只小蝗虫在蟾蜍眼前晃动，逗引这只蟾蜍，观察蟾蜍的反应．
将实验的结果记录在表格中；
| 实验步骤 | 实验现象 |
| 1 | 蟾蜍立即张开口把小蝗虫吃掉 |
| 2 | 蟾蜍仍是张口去吞，但大野蜂蛰了一下蟾蜍的舌头，蟾蜍立刻把大野蜂吐了出来． |
| 3 | 蟾蜍伏着头部予理睬 |
| 4 |
问题思考：
（1）实验步骤1.2说明了蟾蜍有捕食昆虫的本能，这是______行为．
（2）实验步骤3说明了蟾蜍通过生活经验，对大野蜂有了识别，因而不再吞吃，这是______行为．
（3）实验步骤4显示出蟾蜍并没有吃饱，这证明了蟾蜍在实验过程中确实建立起的______（行为）