when l was young,l used ...(swim) in that river.用所给动词的恰当形式填空.

问题描述:

when l was young,l used ...(swim) in that river.用所给动词的恰当形式填空.

when l was young,l used (to swim) in that river.
注:固定用法used to do sth 过去常常做某事
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