【题目】在遛狗的时候，你不慎松开了，结果狗被汽车撞了。
While the dog, you were careless and it got loose and was hit by a car.

【答案】walking
【解析】考查动词短语。walk the dog”遛狗“，此句为时间状语从句中，省略了主语，谓语动词要用非谓语形式，因为表主动意义，故用doing形式。故填walking。