Answer: He was going to buy three things: chairs, tables, and utensils.
Explanation:
The most basic rule for using commas is that they are used to separate independent clauses joined by coordinating conjunctions (and, but, for, or, nor, so, yet).
However, it might be difficult to remember that this rule still applies when we want to separate three or more words, phrases, or clauses written in a series. We must not forget to place a comma before "and".
