Language is a city, to the building of ________ every human being brings a stone.

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We managed to find a boat, ________ we could get to the island.

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I shall never forget those years ________ I lived in the country with the farmers, ________ has a great effect on my life.

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Recently I bought an ancient Chinese vase, ________ was very reasonable.

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The result of the experiment was very good, ________ we hadn't expected.

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John said he'd been working in the office for an hour, ________ was true.

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Dorothy was always speaking highly of her role in the play, ________, of course, made the others unhappy.

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________ is known to us all, the moon travels around the earth once every month.

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The students in the language school are offered a chance to learn ________ second foreign language ________ English.

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________ most of the spelling mistakes can be avoided.

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A．Checking your composition carefully

B．Check your composition carefully

C．If you check your composition carefully

D．Your composition is carefully checked