My grandfather wants ________ around the world because he enjoys ________ new places.

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--- John, will you please ________ the blackboard now? It's your duty.

--- OK.

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If we all make a contribution to ________ the environment, the world will become much more beautiful.

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He was ________ sad at the bad news that he could hardly say a word.

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Today the forests have almost gone. People must ________ down too many trees.

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A．stop from cutting

B．stop to cut

C．be stopped from cutting

D．be stopped to cut

--- I feel tired and sleepy.

--- Why not stop ________?

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