题目内容：

Aids is said_____ the biggest health challenge to both men and women over the past few years.
A.that it is B.to be C.that it has been D.to have been

优质解答

据说…… 有两种表达法：1 sth is said to be 2 It is said that+从句
又句中有明显的暗示：over the past few years 固定用完成时.所以选D.
C 应该为：It is said that aids has been the biggest health challenge
to both men and women over the past few years.