【题目】It was not until midnight ______ the parents finally found their lost kids.
A.that
B.when
C.while
D.as

【答案】A
【解析】句意：直到午夜父母才发现他们丢失的孩子。这里使用特殊的强调句：It was not until…that…，强调的是not until引导的时间状语从句，所以选A。