13. He ____ have completed his work; otherwise,he wouldn't be enjoying hirnself by the seaside.(2005北京)

　　A. shouldB. must

　　C. wouldn'tD. can't

　　【解析】選A根據(jù)下文“否則他在海邊沒法玩得痛快。”可以推出上一句“他本應(yīng)該要完成他的工作。”should have done表示后悔或責(zé)備，意為“本應(yīng)該做了(但事實(shí)上沒做)”。

　　14. I ____ have been more than six years old when the aecident happened. (2005天津)

　　A. shouldn'tB. couldn't

　　C. mustn'tD. needn't

　　【解析】選B“情態(tài)動(dòng)詞 + 完成時(shí)態(tài)”用來(lái)表示對(duì)過去某一事實(shí)的假設(shè)或推測(cè)。尤其用來(lái)表示否定的推測(cè)則"can't / couldn't have done"。本句譯為：當(dāng)事故發(fā)生時(shí)我不可能大于六歲。