问题
It is not until recently ______ thescientists have found proof of there being water on Mars.
A:when
B:that
C:how
D:what
B:that
C:how
D:what
正确答案是：
同类题型
________ terrible weather it was when tsunami and earthquakes happened in Japan.
____ it is to play football on such a cool afternoon
The engine of the ship failed and the bad weather ______ the helplessness of the crew at sea.
______ where to have a picnic for several days，the big family finally made a decision.