18given过去分词短语作状语19where引导定语从句20is tried其他时态也可以。主语是单数,谓语是被动语态。21was being written因为有特定的时间,故应该用进行时。22stayed。would rather后接句子时要用虚拟语气(用过去式表示与现在或将来情况相反)再如I’d rather you came next Saturday. 我宁愿你下星期六来。23is being rebuilt。根据主句意思,原因状语从句的谓语应该用现在进行时的被动语态