Everypossiblemeanstopreventair

Every possible means __________ to prevent air pollution, but the sky is still not clear.

A．are being used

B．have been used

C．has been used

D．had been used

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相关试题

Once upon a time, a （n）__________ famous scientist said that life was not easy for any of us but first of all we should believe in ourselves.

A．another

B．sure

C．some

D．certain

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He let me repeat his instructions __________ sure that I understood what was __________ after he went away.

A．to make; to be done

B．making; doing

C．to make; to do

D．making; to do

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David couldn't tell __________ from far away whether the green traffic light meant going straight or turning left.

A．on purpose

B．at random

C．in short

D．for sure

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-Are you a volunteer now?
-No, but I __________. I worked for the City Sports Meeting last year.

A．used to

B．used to be

C．used to do

D．was used to

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He used to __________cards, but now he is used to __________ a walk after supper.

A．play; taking

B．playing; take

C．play; take

D．playing; taking

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