(2013·吉林长春高中毕业班第一次调研)Many athletes are clear that the Olympic Games are the only time ________ they will be watched by thousands of millions.

Pollution is a serious problem. Scientists have _______ some good ways to save it.

Why did you vote for Maggie—Because she is very ______. She always sharesthings with others.

I traveled to Africa last summer and I saw a lot of wild animals.– ____________ unforgettable experience you had!

The whole building _____ burned down, but the heavy rain _____.