1、 if she could help you ,she would help you.（如果她能帮你，她一定会的）
2、 John stopped studying. =John is not going to study anymore.
3、 John stopped to study. =John stopped doing sth. In order to study.
4、 I have just finished my work.（表示刚刚完成的动作）
5、 He has gone to America.（他去了美国。）（表示结果持续至今）
6、 He has been to America.（他曾去过美国。）（至示曾经有过的经验）
7、 He has lived here for a year.（表示持续到现在的行为）
8、 I enjoyed the movie very much. I wish I had read the book from which it was made.
1、 I sometimes stay up till midnight.(一般现在时)
2、 She's always helping people.(现在进行时)
3、 He is going to change his job.（一般将来时）
1.I bought a new house, but I _________ my old one yet, so at the moment I have two houses.
A.didn't sell B.sold C. haven't sold D.would sell
答案：C. haven't sold。
B) 表示从过去某时刻开始，持续到现在的动作或情况，并且有可能会继续延续下去。此时经常用延续性动词。时间状语常用since加一个过去的时间点，或for 加一段时间，或by加一个现在时间。
2.The conference __________ a full week by the time it ends.
A. must have lasted B. will have lasted C. would last D. has lasted
本题考核谓语动词的时态。全句的意思是：“会议从开始到结束将持续整整一个星期。”句中by the time it ends表示动作要延续到将来某一时刻，因此要用将来完成时。答案是B) will have lasted。如果选A)，因为情态动词must后面接动词不定式的完成时形式表示对已经发生的事情的一种肯定推测，而本句的时间状语是by the time it ends而非by the time it ended，所以犯了时态不呼应的错误。Would虽可以表示推测或可能性，但would last不能表示延续到将来某一时刻的动作，所以C) would last错误。因为D) has lasted是现在完成时，表示到现在为止已经完成的动作，不能表示延续到将来某一时刻的动作，所以也不正确。
（ ）1.He often______his clothes on Sundays.
A. washing B. washes C. has washed D. wash
（ ）2.I’m Chinese. Where______from?
A. do you come B. you are coming C. you come D. are you coming
（ ）3.May______to school.
A. never walks B. is never walking C. walk never D. never is walking
（ ）4.We will start as soon as our teacher______ .
A. comes B. will come C. come D. is coming
（ ）5.How long ago______playing football?
A. have you stopped B. had you stopped C. did you stop D. do you stop
（ ）6.It______ hard when I left my house .
A. is raining B. rains C. was raining D. will rain
（ ）7.I think this question______to answer.
A. easy B. is easy C. was easy D. will easy
（ ）8. Don’t talk so loudly . Your father______.
A. sleeps B. is sleeping C. slept D. had slept
（ ）9.How many people does the doctor know who______of the disease (疾病)？
A. are dying B. is dying C. has died D. dies
（ ）10.I______my homework now.
A. finish B. finished C. have finished D. had finished
答案：1. B 2. A 3. A 4. A 5. C 6. C 7. B 8. C 9. A 10. C