选什么为什么呢?AIDS is said___ the biggest health challenge to both men and women in that area over the past few year.A that it is B to be C that it has been D to have been

问题描述:

选什么为什么呢?
AIDS is said___ the biggest health challenge to both men and women in that area over the past few year.
A that it is B to be C that it has been D to have been

D to have been
首先,be said to be 选择出BD,又因后面 over the past few year.,所以用不定式的完成形式。

D to have been
be said to do 是常见句型.
因为这里有:over the past few year.显然是完成时.
所以要用B的完成时,即D的形式.