Which of the following is a defining feature of a compound sentence?

A compound sentence is characterized by having two or more independent clauses that are connected by a coordinating conjunction (such as "and," "but," or "or") or by a semicolon. This structure allows for a combination of related but distinct ideas within a single sentence, making it more complex than a simple sentence, which contains only one independent clause.

The presence of multiple independent clauses is what distinguishes a compound sentence from other types, such as simple sentences, which have just one independent clause, or complex sentences, which contain at least one independent clause and one dependent clause. Therefore, the defining feature of a compound sentence is indeed the inclusion of two or more independent clauses.