Where do you work? I work in _____________.[ ]
A. at night
B. a post office
C. by bus
答案:B
Did you smell something ____. [ ]
A. burn
B. burning
C. to be burnt
D. being burnt
( )能传递很大的扭矩,常用于重型机械设备中。
A.切向键B.花键C.楔向键D.半圆键