Not having met( not met ) him for a long time,I can not tell you what he is like.

题目

Not having met( not met ) him for a long time,I can not tell you what he is like.
请问为什么要填Not having met?而不是Don’t meeting?

答案

这是现在分词的否定式【Not +v-ing】,作状语表原因
由于很久没见到他了,所以没法同你讲清楚他长得怎么样了.
由于分词having met 是先于谓语can't tell 发生的,故用现在分词的完成式
等于：
【Because I haven't met him for a long time】,I can not tell you what he is like.