问题

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

正确答案是：

同类题型

It was not until the beginning of the twentieth century_______ to explore space. [ ]

Is this the reason ______ at the meeting for his carelessness in his work?

We should know that we can only reach the top if we are ready to and learn from failure.

_____I live I must serve the people heartand soul.

Mr Smith will leave school after he ________ his work this afternoon.