选什么为什么呢?
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
答
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.