一、must +現(xiàn)在完成時

　　表示對已發(fā)生的事情的一種肯定的猜測。

　　1、Mr. Green _____ my letter， otherwise he would have replied before now.

　　A. must have received　　B. must have failed to receive

　　C. must receive 　　D. must fail to receive

　　(答案：B)(1998年44題)

　　2、I believe he _____ an accident， otherwise he would have arrived on time.

　　A. would have had　 　B. could have had

　　C. should have had　　D. must have had

　　(答案為D)(2001年58題)

　　二、should (ought to )+完成時

　　表示應該做的事情而沒有做，否定式表示不該做的事情做了。含有對過去的動作的責備、批評。

　　1、They have done things they ought _____.

　　A. not to do　 B. not to be done

　　C. not to have done　　D. not having done

　　(答案為C)(1999年59題)

　　2、I'm sorry I couldn't get in touch with him before he left， I _____ him earlier.

　　A. had a telephone　 　B. have phoned

　　C. should have phoned　　D. should be phoned

　　(答案為C)(2000年26題)

　　三、could +完成時

　　表示能做的事情而沒有做。表示對過去能做而未做的事情感到惋惜，遺憾。

　　1、He could have joined us， but he didn't get our invitation in time.

　　他本來能夠參加我們的，但是他沒有收到我們的請貼。

　　2、I could have passed， but I did not study hard enough.

　　我本來能及格的，但是沒有努力學習。