Which part of a clause is not necessary for it to function on its own?

In a clause, a subordinating conjunction is not necessary for it to function independently. A clause can stand alone as a complete sentence when it contains at least a subject and a verb expressing a complete thought. Independent clauses, for instance, generally consist of a subject and a predicate, which includes the verb.

The role of a subordinating conjunction is to link a dependent clause to an independent clause, creating a relationship between them. Since it serves to join clauses rather than constituting the foundational elements of a clause itself, its presence is not required for a clause to function independently.

In contrast, the subject and verb (as components of the predicate) are essential elements of a clause. Without a subject, there is no entity performing the action, and without a verb, there is no action or state of being conveyed. Therefore, the subordinating conjunction is not a requirement for a clause to be complete, making it the correct answer to the question.