1. 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引导的与过去相反的虚拟。

2. 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是过去式，所以该句是由as though引导的与过去相反的虚拟。

3. 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引导的与现在事实相反的虚拟。

4. He described the town as if he ______ it himself.

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

解析：A.as if引导的与过去相反的虚拟。

5. 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后接从句要求用虚拟语气，形式为过去式，表示对现在或将来的假设，或为过去完成式表示对过去的情况的假设。6. 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引导的定语从句中的现在完成时表示动作业已发生，所以主句中表示的虚拟是针对已经发生了的行为，所以应该用过去完成式表示对过去的虚拟。

7. 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)这是一人含蓄虚拟条件句，通过介词短语without,表示潜在的一种假设，而主句中的情况也早已经发生，所以是对过去情况的一种假设，因此用would not have been achieved这一形式。

8. 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)连so that引导的从句中要求用虚拟语气，表示一种假设，形式为might+动词原形。

9. 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是一种要求从句用虚拟语气的常见句型。虚拟语气形式为动词的过去式。

10. 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用来表示一种含蓄的虚拟假设，因为是对过去(yesterday)的情况的假设，所以应该用would have come形式。