OpenSAT

Question #N1173

The use of commas in a series of three or more items is a common convention in Standard English. However, there are some cases where the comma before the conjunction "and" in a series is optional. The rule of thumb is that the comma is needed if omitting it would cause confusion or ambiguity. For example, in the sentence "The guests ate the main course, dessert, and coffee", the comma is not necessary because there is no risk of ambiguity without it. However, in the sentence "The guests ate the main course, dessert, and coffee, which was served in a fancy teacup", the comma is necessary to prevent the reader from misinterpreting "and coffee, which" as a phrase modifying "dessert." The comma is also necessary when the final item in the series is a long phrase or a clause. For example, in the sentence "The guests ate the main course, dessert, and a cup of coffee that was brewed especially for the occasion", the comma before "and" is needed because the final item in the series is a long phrase.