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.  

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

$ P3 E1 l& u; c' Q$ p: t没有接句子
it is necessary to have done sth.
接了个完成时的动宾结构

# w( Q8 h1 ~2 F+ y2 N) w6 b你可以对比一下下面两句的含义
it'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.
. H% c! x9 h! n* ?9 y6 u: f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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