About 70 percent of the population ______ in that country in the mountains and only 30 percent of its land ______ farmland.

单项选择题—You'd better ______ work too hard like this. —I see. You mean ______ too hard makes one tired and ill.

单项选择题So far nobody has claimed the money （） in the library.

A. discovered
B. to be discovered
C. discovering
D. having discovered

单项选择题They used to quarrel a lot, but now they are completely ______ with each other.

单项选择题We （） on this project for four hours. Let's have a rest.

A. are working
B. have been working
C. worked
D. had worked

单项选择题There is a ______ of impatience in the tone of his voice.