问题
选择题
The library needs ＿＿, but it will have to wait until Sunday．
A．cleaning
B．to clean
C．clean
D．being cleaned
答案
A
need后接动名词作宾语，常以主动形式来表示被动意义。
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The library needs ＿＿, but it will have to wait until Sunday．
A．cleaning
B．to clean
C．clean
D．being cleaned
A
need后接动名词作宾语，常以主动形式来表示被动意义。
和变化周期T都是已知量，求：