问题
单项选择题
Our holiday plans（）because of transport strikes.
A.fell out
B.fell through
C.fell over
D.fell behind
答案
参考答案：B
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Our holiday plans（）because of transport strikes.
A.fell out
B.fell through
C.fell over
D.fell behind
参考答案：B
，则f'(5)为( )．