It is well understood _____ controls the flow of carbon dioxide in and out the a

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It is well understood _____ controls the flow of carbon dioxide in and out the atmosphere today.

A．that

B．when

C．what

D．how

答案

解析

略

举一反三

No sooner had we reached the top of the hill _____ we all sat down to rest.

A．when

B．then

C．than

D．until

题型：不详难度：| 查看答案

The reason for the party was _____ it was Sue’s birthday.

A．because

B．that

C．because of

D．due to

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_____ quite recently, most mothers in Britain did not take paid work outside the home.

A．Before

B．Until

C．From

D．Since

题型：不详难度：| 查看答案

I have kept that portrait _____ I can see it every day, as it always reminds me of my university days in London.

A．which

B．where

C．whether

D．when

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You see the lightning _____ it happens, but you hear the thunder later.

A．the instant

B．for an instant

C．on the instant

D．in an instant

题型：不详难度：| 查看答案