20. When Jack arrived he learned Mary for almost an hour.A. had goneB. had set offC. had

问题补充：

20. When Jack arrived, he learned Mary for almost an hour.

A. had gone

B. had set off

C. had left

D. had been away

答案：

A. had gone

B. had set off

C. had left

(答案→)D. had been away

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