Onlyaftertheyhadperf的精選

問題詳情： Onlyaftertheyhadperformedhundredsofexperiments_____insolvingtheproblem.A.didtheysucceedB.theysucceeded    C.hadtheysucceeded  D.theyhadsucceeded【回答】A知識點：倒裝與省略題型：選擇題...