Onlyaftertheyhadperf的精选

问题详情： Onlyaftertheyhadperformedhundredsofexperiments_____insolvingtheproblem.A.didtheysucceedB.theysucceeded    C.hadtheysucceeded  D.theyhadsucceeded【回答】A知识点：倒装与省略题型：选择题...