Onlywhentheyhadn’theardfromherforalongtime

问题详情：

 Only when they hadn’t heard from her for a long time ________ to doubt whether something bad had happened to her.

A. they began              B. did they begin         C. they had begun         D. had they begun

【回答】

B

知识点：倒装与省略

题型：选择题