_________ that mistake once，I shall not make the same mistake again．

[　　]

An army spokesman stressed that all the soldiers had been ordered _________ clear warnings before firing any shots．

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I can think of many cases ___________ students obviously knew a lot of English words and expressions but couldn't write a good essay．

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Classroom testing, if well done, most certainly ________ a stimulus to study and real learning.

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The sale usually takes place outside the house, with the audience ________ on benches, chairs or boxes.

[　　]

The managers discussed the plan they would like to see________ the next year.

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________ more attention, the tree could have grown better.

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--I stayed at a hotel while in New York.

--Oh, did you? You ________ with Barbara.

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--There were already five people in the car, but they managed to take me as well.

--It ________ a comfortable journey.

[　　]

--Did you see the famous dancer?

--No.

________ you come here a little earlier, you ________ her.

[　　]

A．Had; might have seen

B．Had; could see

C．If; could see

D．If; would have seen