We have got accustomed__________ in an air—conditioned room, so we can’t stand the terrible heat outside.

lived in China for 8 years, Helen has a good____________ of both English and Chinese.

Let’s try our best to ____ paper to savethe trees.

Tom ________ in the library every night over the last three months.[ ]

The_______ you are in the exam, the_______mistakes you will make.