What must a complete sentence contain?

A complete sentence is fundamentally defined as having a subject and a predicate. The subject identifies who or what the sentence is about, while the predicate provides important information about the subject, typically stating what the subject does or what happens to the subject. This structure ensures that the sentence conveys a clear and complete thought.

In contrast, other combinations, such as a subject with a conjunction, a predicate with an object, or a subject with an adverb, do not meet the requirements for a complete sentence because they lack one of the critical elements—primarily the verb that describes the action or state of being of the subject. Without both a subject and a predicate, the sentence remains incomplete and fails to express a full idea. Hence, the correct choice accurately reflects the necessary components for forming a grammatically correct complete sentence.