问题
单项选择题
Not until he left his home ______ to know how important the family was for him.
A．did he begin
B．had he begun
C．he began
D．he had begun
答案
参考答案：A
解析： 句意：直到离开家他才开始了解家对他来说多么重要。not until置于句首，主句要部分倒装，排除C、D两项；又根据句意得知begin需用过去式，但发生在leave之后， 故排除B项。