he met with the difficulty did he realize that our help was of great importance
A. It was only when
B. Never until
C. Only before
D. It was not until
网友回答
A. It was only when
(答案→)B. Never until
C. Only before
D. It was not until
解析：
试题分析:句意：直到他遇到了困难他才意识到我们的帮助非常重要。根据句中的did he realize…判断此处是倒装结构，排除AD选项，而C选项逻辑混乱，故答案选B。