Not until he met with the difficulty the importance of group work．
A. he realized
B. did he realize
C. realized he
D. he didn’t realize
网友回答
A. he realized
(答案→)B. did he realize
C. realized he
D. he didn’t realize
解析：考查倒装句：句意：直到他遇到困难他才意识到团队工作的重要性。Not until+从句放在句首的时候，主句的谓语是部分倒装，选B。