【推荐1】Stephen Hawking's crowning achievement was his prediction in the 1970s ________ black holes can emit energy, despite the classical view that nothing can escape their gravity.

A．when

B．what

C．how

D．that

【推荐2】There is no doubt ______ the fact ______ it is not suitable to grow cash crops here .

A．whether, that

B．that, why

C．if, which

D．about, that

【推荐3】People have no idea ______had happened on the plane.

A．how

B．what

C．which

D．where

【推荐1】It was the training          he had as a young man            made him such a good engineer.

A．what; that	B．that; what
C．that; which	D．which; that

【推荐2】It was until late afternoon          he was figuring out          he considered was a wise way to fight against it.

A．when; what

B．that; that

C．that; what

D．when; that

【推荐3】---It is _____ he often failed in exams _____ makes his parents worried about him.
---- Actually, they needn’t worry so much.

A．what, that

B．that, what

C．that , that

D．/, that