【题目】It was not until all the fish in the pond died that________ the situation was serious.
A. did he realize B. he realized
C. he had realized D. had he realized
在线课程【答案】B
【解析】
试题分析：考查强调句。句意：直到池塘里所有的鱼都死了，他才意识到问题的严重性。强调句结构it is… that，that后接完整句子，故选B项。