4、Theschoolconducteda(n)__________investigationontheaccident. 正确答案:extensiveThismedicine__________beforedinner. 正确答案:shouldbetakenTom _______have kept his promise. I wonder why he changed his idea. 正确答案:shouldWhatIshoulddois__________ thetasksoon. 正确答案:tofinish二、阅读理解:阅