Tom was about to close the window     his attention was caught by a bird.
#92304
A
when   
B
if
C
and   
D
till
推荐题目
______ Marx's works with Engels', and you'll find many differences.
#92685
A
Comparing
B
Compare
C
To compare
D
If you compare
____________, I wouldn’t have finished my homework.
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A
If you didn’t help me
B
Had you not helped me
C
If you haven’t helped me
D
Haven’t you helped me