He ________ full marks, but he was so careless as to make a spelling mistake.

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People try to avoid public transportation delays by using their own cars, and this ________ creates further problems.

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When I try to understand ________ that prevent so many Americans from being as happy as one might expect, it seems to me that there are two causes.

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－Did you notice Mary was busy all day in the office?

－Oh, yes, she has just finished her business tour of Chicago. She has a lot of work to ________.

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With his son ________, the old man felt unhappy.

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________ to the tower building, from where you can see the whole town.

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－What happened to Mr. Smith early this morning?

－Oh, he was seen ________ down the driver and ________ away.

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________, so I had to wait for my wife back.

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A．Because my key was lost

B．My key was lost

C．Losing my key

D．Having lost my key

－________ he clean the classroom now?

－No, he ________. He may do it tomorrow.

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How many of us ________, say, a meeting that is irrelevant (不相关的) to us would be interested in the discussion?

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