标题: 由OG 12 SC 87引发的一个小问题，求指导！ [打印本页] 作者: japlir 时间: 2011-4-4 18:35 标题: 由OG 12 SC 87引发的一个小问题，求指导！ In an effort to reduce their inventories, Italian vintners have cut prices; their wines have been priced to sell, and they are.
(A) have been priced to sell, and they are (B) are priced to sell, and they have (C) are priced to sell, and they do (D) are being priced to sell, and have (E) had been priced to sell, and they have
OG对D的解释中，说omitting the subject they requires that the comma be omitted as well. 对于and前何时用逗号何时不用逗号很疑惑！ 一般三个并列的时候A,B,and C第三个并列元素前不都是要用逗号和并列词and 么？ 彻底困惑了， 求NN帮助区分：什么时候and 前要逗号，什么时候不能要逗号？
A run-on sentence is a sentence in which two or more independent clauses (i.e., complete sentences) are joined without appropriate punctuation or conjunction. It is generally considered to be a grammatical error though it is occasionally used in literature and may be used as a rhetorical device. An example of a run-on is a comma splice, in which two independent clauses are joined with a comma without an accompanying coordinating conjunction.