问题
选择题
_______ he met with the difficulty did he realize the importance of our help.
A．Even though
B．Never until
C．Only before
D．Ever since
答案
B
此题考查从句的引导词。根据主句是倒装did he realize可以排除A、D两项。如果选C项，则主句应该用过去完成时态had he realized,因而被排除。