22.They kept trying _____ they must have known it was hopeless.为什么用WHEN?
问题描述：
22.They kept trying _____ they must have known it was hopeless.为什么用WHEN?
答
when在这里是指“尽管。。。但”吧
答
when 在这里有“尽管.但”的意思,尽管他们一定知道那是无用的,但是他们仍然在尽力尝试.