Helen is much more kind to her youngest child than to the others, ________of course, makes the others unhappy.

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Look at these tracks（痕迹）. It _______ be a wolf.

It needn't be. It ________ be a fox.

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Do you want tea or coffee?

________. I really don't mind.

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The research is so designed that once _______nothing can be done to change it.

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When I handed the report to John, he said that George was the person ________.

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Great changes ________in the city, and a lot of factories_________.

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A．have been taken place; have been set up

B．have taken place; have been set up

C．have taken place; have set up

D．were taken place; were set up

Excuse me, may I changed this pair of shoes ________a bigger pair?

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After the new technique was introduced, the factory produced _________ tractors in 1988 as the year before.

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A library with five thousand books _______to the nation as a gift.

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That's the same pen ________I lost yesterday.

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