only when they were told of the importance of time ____ wasting t_英语解答

only when they were told of the importance of time ____ wasting time is equal to wasting part of their life.
A.did those boys realize
B.had those boys realized
why not

人气：474 ℃　时间：2019-10-19 22:04:56

解答

b过去完成时,比过去更过去.when引导的从句是过去时,空后面主句的时态在从句发生后才发生.若选b,时间关系上就不对.如果这里把had改为have可以吗？很不合适，only when 倒装句型主句从句时态一致。