I wonder why Jenny ________ us recently. We should have heard from her by now.

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Although he has lived with us for years, he ________ us much impression.

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How many years ________ he ________ Mary?

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Selecting a mobile phone for personal use is no easy task because technology ________ so rapidly.

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Mary’s mother ________ every time we go to see her.

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--I wonder if Mary ________ our conference.

--So do I. I’ll ring you up if she ________.

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I don't think ________ possible to master a foreign language without much memory work.

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It was in the lab ________ was taken care of by Professor Harris ________ they did the experiment.

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A ________ expression appeared on her face when she learned his ________ bicycle had been stolen.

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After half a year's training, they were made to be used ________ underwater.

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