Is Mrs White in the office? Yes,_she is on duty,she must be here. A.since B.until C. while D.if
问题描述：
Is Mrs White in the office? Yes,_she is on duty,she must be here. A.since B.until C. while D.if
答
选C.
这段对话的汉语意思是：有人问怀特夫人在办公室吗?是的,因为今天她值班,他一定会在办公室的.“while”有“因为,由于”的意思,其他选项都不符合语境.