21. As usual, he put on a show as though his trip a great success.

　　A. had been B. has been C. were D. was

　　解析：A.as though引導(dǎo)的與過去相反的虛擬。

　　22. Looking round the town, he felt as though he away for ages.

　　A. has been B. was C. is D. had been

　　解析：D.felt是過去式，所以該句是由as though引導(dǎo)的與過去相反的虛擬。

　　23. John is so strongly built that he looks as if he as elephant.

　　A. lifts B. is lifting C. lifted D. could lift

　　解析：D.as if引導(dǎo)的與現(xiàn)在事實相反的虛擬。

　　24. He described the town as if he it himself.

　　A. had seen B. has seen C. saw D. sees

　　解析：A.as if引導(dǎo)的與過去相反的虛擬。

　　25. Most insurance agents would rather you anything about collecting claims until they investigate the situation.

　　A. do B. don’t C. didn’t D. didn’t do

　　解析：(D)would rather后接從句要求用虛擬語氣，形式為過去式，表示對現(xiàn)在或?qū)�來的假設(shè)，或為過去完成式表示對過去的情況的假設(shè)。

　　26. Although most adopted persons want the right to know who their natural parents are, some who have found them wish that they the experience of meeting.

　　A. hadn’t B. didn’t have had C. hadn’t had D. hadn’t have

　　解析：(C)who引導(dǎo)的定語從句中的現(xiàn)在完成時表示動作業(yè)已發(fā)生，所以主句中表示的虛擬是針對已經(jīng)發(fā)生了的行為，所以應(yīng)該用過去完成式表示對過去的虛擬。

　　27. Without electronic computers, much of today’s advanced technology .

　　A. will not have been achieved B. have not been achieved

　　C. would not have been achieved D. had not been achieved

　　解析：(C)這是一人含蓄虛擬條件句，通過介詞短語without,表示潛在的一種假設(shè)，而主句中的情況也早已經(jīng)發(fā)生，所以是對過去情況的一種假設(shè)，因此用would not have been achieved這一形式。

　　28. He told her to return the book in time so that others a chance to read it .

　　A. may have B. will have C. would have D. might have

　　解析：(D)連so that引導(dǎo)的從句中要求用虛擬語氣，表示一種假設(shè)，形式為might+動詞原形。

　　29. It is time that the government measures to protect the rare birds and animals.

　　A. takes B. took C. has taken D. taking

　　解析：(B)It is time that是一種要求從句用虛擬語氣的常見句型。虛擬語氣形式為動詞的過去式。

　　30. He was very busy yesterday, otherwise he to the meeting.

　　A. would come B. came C. would have come D. had come

　　解析：(C)otherwise用來表示一種含蓄的虛擬假設(shè)，因為是對過去(yesterday)的情況的假設(shè)，所以應(yīng)該用would have come形式。

　　31. I must say he reads very well, and I shouldn’t be surprised if he acting for a living one day.

　　A. had taken up B. takes up C. have taken up D. would have taken up

　　解析：(B)所給的四個選項中沒有一個表示對未來的情況的虛擬的形式should+動詞原形，或是were to do，因此可以斷定if引導(dǎo)的條件句在這里最真實的條件句，用一般現(xiàn)在時表示一般將來時，故(B)是正確答案。

　　32. If I had seen the movie, I you all about it now.

　　A. would tell B. will tell C. have told D. would have told

　　解析：(A)這是一個混合虛擬語氣的句子，if條件句表示的是對過去情況的假設(shè)，而主句是對現(xiàn)在(now)的情況的假設(shè)，故用would tell形式。

　　33. I’d rather you anything about it for the time being.

　　A. do B. didn’t do C. don’t D. didn’t

　　解析：B.would rather引導(dǎo)的虛擬語氣其謂語用過去式。

　　34. Mary my letter; otherwise she would have replied before now.

　　A. has received B. ought to have received C. couldn’t have received D. shouldn’t have received

　　解析：C.注意單詞otherwise引導(dǎo)虛擬語氣。

　　35. We didn't know his telephone number, otherwise we _____ him. ( 1995年6月四級第46題)

　　A) would have telephoned 　　B) must have telephoned C) would telephone 　　D) had telephoned

　　解析：本題是與過去時相反的虛擬句，從句中用過去完成式，主句中用would have done。本句相當(dāng)于if we had known his telephone number，we would have telephoned him。答案是(A) would have telephoned。