California Teacher Credentialing Examination (CSET) Practice Test 2025 - Free CSET Practice Questions and Study Guide

A comma is needed before a coordinating conjunction primarily in compound sentences. A compound sentence consists of two or more independent clauses that are joined by a coordinating conjunction such as "and," "but," "or," "nor," "for," "so," or "yet." The comma is used to separate the two independent clauses to clarify the sentence structure and guide the reader through the thoughts being connected.

For instance, in the sentence “I wanted to go for a walk, but it started raining,” the comma before "but" indicates a pause and helps to inform the reader that there are two distinct independent clauses being combined.

In contrast, the other options do not accurately represent the rules concerning the use of a comma with coordinating conjunctions. Specifically, a comma is not necessary in sentences that merely list verbs, nor is it required in every sentence structure or across all lists. In lists, for example, a comma is used to separate items, but the use of a comma before a coordinating conjunction in that specific context would depend on specific stylistic choices (such as the Oxford comma) rather than being a strict grammatical necessity.