AIDS is said the biggest health challenge to both men and women in the earth over the past four years.
A. that it is
B. to have been
C. that it has been
D. to be
网友回答
A. that it is
(答案→)B. to have been
C. that it has been
D. to be
解析：考查固定句型。sb/sth is said to do sth据说某人/某物做了某事，当两个动作发生有先后关系时，用不定式的完成时，即to have done。句意：在过去的四年里，据说艾滋病已经是威胁男性和女性健康的最大的因素。over/in the past... years“在......过去的几年里”，常与现在完成时连用，关系B。