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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* c' L/ n( e% B# l0 |6 F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

9 k6 |& I  P3 z没有接句子
2 U6 k6 t3 B5 H8 n5 R+ l0 ]it is necessary to have done sth.
接了个完成时的动宾结构

* r/ C: u1 E$ F你可以对比一下下面两句的含义
! g% Y) g7 N* D2 c9 xit's necessary to acquire this.
有必要（现在或以后）去获取这个
it's necessary to have acquired this.
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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