Onlywhentheyhadn’theardfromherforalongtime

問題詳情：

 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

知識點：倒裝與省略

題型：選擇題