第1个回答 2012-10-28
不能直译，参考如下：
It's necessary to do
There is a need to do
doing sth is necessary
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第2个回答 2012-10-28
It is nessary to do sth.
第3个回答 2012-10-28
it is necessary to do sth
第4个回答 2012-10-28
It is necessary to do sth.
Doing sth. is necessary.本回答被提问者采纳