阅读下面材料，在空白处填入适当的内容 (1个单词) 或括号内单词的正确形式。

If you go out to the fields at night in spring or summer, you can hear frogs singing 【小题1】(happy) here and there. It seems as if they were performing a field group singing.

The frog is a good and useful creature that benefits human beings. They can catch fast-moving 【小题2】 (insect). Each frog eats a large number of pests (害虫) that are 【小题3】 (harm) to crops. This little creature is regarded as “the natural enemy of pests”.

But now frogs 【小题4】 (get) fewer and fewer. This is 【小题5】 they are killed and put on the table as a delicious dish by their chief enemy, human beings. It is a shameless and cruel act, isn’t it?

The cause that is responsible 【小题6】 the rapid reduction of frogs is that farmers use insect killers to kill pests and frogs get killed as a result of drinking poisoned water while 【小题7】 (eat) poison-killed insects.

Something must be done as soon as possible 【小题8】 (save) frogs. If we don’t punish those 【小题9】 sell and kill frogs to make money, then one day all of us 【小题10】 (punish) by nature for failing to keep them.