Not until he left his home to know how important the family was for him. A. had he begunB

问题补充：

Not until he left his home to know how important the family was for him.

A. had he begun

B. did he begin

C. he began

D. he had begun

答案：

A. had he begun

(答案→)B. did he begin

C. he began

D. he had begun

解析：考察倒装句。Not until放在句首的时候，后面的句子使有部分倒装的形式，故排除CD。再看时态，本句不需要使用过去完成时。句意：直到他离开家，他才知道家对他来说是多么重要。