. he used to go skiing in winter but now swimming is his favorite.A. At a timeB. At one ti

问题补充：

. he used to go skiing in winter but now swimming is his favorite.

A. At a time

B. At one time

C. At no time

D. At times

答案：

A. At a time

(答案→)B. At one time

C. At no time

D. At times

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