Carbon dioxide（）from burning fuels is the most common of the so-called green-house gases.

单项选择题—Ring me at 5 am. No, better not so early ! I（）.—I got it.

A. will sleep
B. sleep
C. am sleeping
D. will be sleeping

单项选择题The old man who（）in the deserted house alone tbr ten years has been settled in a nursing home now.

A. lived
B. had lived
C. has lived
D. has been living

单项选择题Every camera we sell comes with a two-year（）

A. guarantee
B. safety
C. confirmation
D. conservation

单项选择题（）a moment and I will go to your rescue.

A. Go on
B. Hold on
C. Move to
D. Carry on

单项选择题Tough as the task was, we（）finish it ahead of time and therefore we were highly praised for it.

A. would
B. had to
C. were able to
D. must