to 后面可接句子吗？

xixiokok

In order to design policies that aim to change commuting practices it is, however,necessary to have acquired a good understanding of the trips in question and their determinants.  
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这句话里，necessary to 后面为什么可以接 have acquired a ...句子？

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江南一屁

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it is necessary to have done sth.
接了个完成时的动宾结构
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/ v- F6 D& z* z! X0 i你可以对比一下下面两句的含义
it's necessary to acquire this.
) c3 u9 q0 A4 y) J有必要（现在或以后）去获取这个
3 ~+ M: G2 M! O; |$ z, Mit's necessary to have acquired this.
) s, {, K7 E* q! D( @% g2 ]2 m* x有必要目前已经获取了这个（具有这个是有必要的）
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