All flightsbecause of the snowstorm many passengers could do nothing but take the train .

问题补充：

All flightsbecause of the snowstorm, many passengers could do nothing but take the train .

A. had been canceled

B. have been canceled

C. having been canceled

D. being canceled

答案：

A. had been canceled

B. have been canceled

(答案→)C. having been canceled

D. being canceled

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