appear强调自身表现出，流露出；
seem是别人从一些现象分析出；
look是从外表，外貌上看出；
1：look,seem可后接like介词短语，appear不能！
2：look可用于sb look as if...及it lokks as if...；而seem/appear后跟从句时，主语只能是it!!
3：look,seem可后接as if/though从句，appear较少出现这种情况！！
4：appear,seem可后接that从句，look不能！！
5：appear,seem可后接不定式，look不能！！
6：appear,seem可用于there引导的结构中，look不能！！
巩固练习：
1.He _____to be your friend but I doubt if he is.
A. looks B. seems B. appears D. is appearing.
2.There _____to have been a house here.
A. seems B. looks C. appears D. A and B
3.He knows Harbin very well. It _____as if he had been there before.
A. seems B. is appearing C. looks D. A and C
4.Tom:Is it already three o’clock?
Mary: Yes. It _____that we won’t get there on time.
A. seems B. looks C. had appeared D. has looked
5.It _____like months ______he left for the United States. I have been missing him very much. A. looks, before B. seems, since C. appears, when D. seems, after
6.You seems ______this film before because you could tell us about it in class.
A. to have seen B. to see C. having seen D. to be seen
7.Mary: Do you know why he _____very sad these days?
Tom: Well. His father passed away last week.
A. has been seeming B. is appearing C. has been looking D. has seemed
8. He _____very happy because he passed the exam this time.
A.seemed B. looked to be C. appeared D. All of above
9. Which of the following is wrong? ______.
A. It appears that he has many friends in Beijing.
B. He appears to have many friends in Beijing.
C. It appears to me that he has never read this novel.
D. It appears like years since he went west.
10.Which of the following is wrong? ______.
A. It seems as there will be an election soon.
B. There seem to be hope that business will get better.
C. It would not seem proper to do so.
D. He seemed to have been an actor.
参考答案：
1. C 2. D 3. D 4. A 5. B 6. A 7. C 8. D 9. D 10. B
注：第10小题中的C would seem比seems说话的语气更婉转
参考资料：http://blog.sina.com.cn/s/blog_531f98e30100mhux.html