偶到网上去找了找, 好象这个有点意思
http://www.grammarbook.com/
应该是美国人的书, 上头的东动有点意思, 可以参考一下
Rule 11. If something or someone is sufficiently identified, the description following it is considered nonessential and should be surrounded by commas.
Example Freddy, who has a limp, was in an auto accident.
Freddy is named so the description is not essential.
The boy who has a limp was in an auto accident.
We would not know which boy is being referred to otherwise; therefore, no commas are used.
Rule 12. Using a comma is optional to separate two sentences joined by a coordinating conjunction—and, or, but, for, nor.
Example I have painted the entire house, but he is still working on sanding the doors. OR
I have painted the entire house but he is still working on sanding the doors.
Rule 13. Use the comma to separate two sentences if it will help avoid confusion.
Example I chose the colors red and green, and blue was his first choice.
Rule 14. If the subject does not appear in front of the second verb, do not use a comma.
Example He thought quickly and still did not answer correctly.
The subject does not appear after the and, so no comma is used.
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