DNA is very useful for us, it many years ago.

A. discovers

B. discovered

C. is discovered

D. was discovered

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14．---Can you come on Monday or Tuesday，Scott？---I'm afraid_____ possible．I'll be on business on those two days．（　�。�
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—What do you and your cousin ______?

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Ted, my little brother, is in Grade One. Last Friday he came back from school with a letter. The letter was from his teacher. “I got a red flower today. Could you please sign this note?” he said to mum. The note showed that he had been talking in class.21cnjy.com

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B. Because he did something wrong.

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D. Because the teacher thought he was too lazy.

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3.

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3．Look at our new school．It ____ last year．（　　）
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