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Getting to other planets or to the moon _____ many problems.

A.involve　　　 B. involves 　 C. involving　　 D.to involve

What caused the accident ______ on the road.

A.were stone　 B. were stones　　 C. was stone　　 D. was stones

When and where to build the new factory _____ yet.

A.is not decided  　B.are not decided   C.has not decided　　　 　　　D.have not decided

In that country, the rich ______ richer, the poor, poorer.

A. become　　 B. has become　　　 C. becomes　 D. is becoming

The wounded _______ by the hospital.

A.have been taken in　　　B.has been taken in    C.have taken in　  D.has taken in

 The youth of China today ___ trying their best to study modern science and technology.

A.is  B.was     C.were    D.are

Cattle ______ on the hillside.

A.grazes          B. is grazing         C. was grazing   D. were grazing

His family _____ always quarrelling among ______.

A.is；itself     B.are；themselves

C.is；themselves    D.are；itself

　The public ______ generous in their contributions to the earthquake victims.

A.is　　　　　　　 B. was　 C. are　　　　　　 D. has been

The committee ______ over the problem among themselves for two hours.

A.has argued    B. has been arguing    C. have argued    D. have been arguing