While the dog you should take care not to get loose . Otherwise it may be dangerous to

问题补充：

While the dog, you should take care not to get loose . Otherwise, it may be dangerous to strangers.

A. walking;

B. walked

C. walking for

D. training for

答案：

(答案→)A. walking;

B. walked

C. walking for

D. training for

解析：考查状语从句的省略。“在遛狗时注意不要松手，否则狗会威胁到陌生人。”While （you are）walking the dog---