问题补充：
, I was so careless that it got loose and was hit by a car.
A. While I walked the dog
B. While I walking the dog
C. While walking the dog
D. While I am walking the dog .
答案：
A. While I walked the dog
B. While I walking the dog
(答案→)C. While walking the dog
D. While I am walking the dog .
解析：考查状语从句的省略式，英语中，主从句deep主语一致可以省略从句的主语和be动词While walking the dog= While I was walking the dog，句意是：我在遛狗的时候很粗心，松开它，结果被车撞了。选C。
