AIDS is said ______ the biggest health challenge to both men and women in that area over the past few years.

A.that it is

B.to be

C.that it has been

D.to have been

答案及解析： D

解析：

句意：据说，在过去的几年中，艾滋病对于那个地区的男女来说已是最大的挑战。It is said that从句可转为sb./sth. be said to do/to be doing/to have done的形式。由此可淘汰A、C两项，由于句子中的时间状语over the past few years要用完成时，所以淘汰B项选出正确答案D。