题目内容：

Complete the sentences with the given words in their suitable forms. (共8分)

1.Some parents purchase new _______________ (toy) for their kids before Christmas.

2.All the classmates took the difficult exam, but only _______________ (fifth) of them passed.

3.They were proud to say these paintings belonged to _______________ (they).

4.The professor made an interesting _______________(speak) at the meeting. 

5.Children were fond of reading _______________ (excite) stories in their free time. e

6.They had a(n) _______________ (happy) trip because of the bad weather.

7.PM2.5 is _______________ (main) caused by air pollution in some parts of the country.

8.The doctor is ready to _______________ (operation) on his broken leg.