. Getting to other planets or to the moon _____ many problems.A．involveB．involve

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

A．involve

B．involves

C．involving

D．to involve

答案

解析

略

举一反三

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

A．become

B． has become

C．becomes

D．is becoming

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. Not one in one hundred children exposed to the disease ______ likely to develop it.

A．should be

B．must be

C．is

D．are

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．Mother ______ us stories when we were young .

A．was used to tell

B．is used to telling

C．used to tell

D． used to telling

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Every possible means ____, but none ____ successful．

A．has tried; has proved	B．tried; proves
C．has been tried; proves	D．is being tried; is proved

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.More patients ＿＿　in hospital this year than last year.

A．treated

B．have treated

C．had been treated

D．have been treated

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