I had just started back for the house to change my clothes _

I had just started back for the house to change my clothes ____ I heard voices.
I had just started back for the house to change my clothes ___________ I heard voices.
A) as B) when C) after D) while
为什么不选while?或者as?

B)
while是在...期间,它引导的句子的动词是延续性的,往往用进行时态表达,而本句中的heard是暂时性动词；as是当...时,表明两个动作同时发生,但本句中的两个动作是先后发生的,故错误；when的词义是“在此时、当...的时候”