1 . Their research focuses on the___________ (solve) to environmental pollution. (所给词的适当形式填空)

2 . Attempts to find a __________(解决方法) is failed.(根据汉语提示单词拼写)

3 . He was allowed to go out,but his parents made it a_____that he should get home before midnight.

A．solution

B．condition

C．state

D．situation

4 . The ________(solve), of course, was to plant trees so the animals could seek shelter during the daytime.   (所给词的适当形式填空)

5 . He tried hard to find the s________ to the problem. (根据首字母单词拼写)