What characterizes a simple sentence?

A simple sentence is characterized by having one independent clause that expresses a complete thought and does not include any subordinate clauses. This means that it contains a subject and a predicate, and although it may have compound subjects or predicates, it remains a single clause.

For example, "The dog barked." is a simple sentence because it has one independent clause. In contrast, a sentence with multiple independent clauses (like compound sentences), one that contains subordinate clauses, or those that ask questions or exhibit complex structures do not fall under the definition of a simple sentence. Thus, the definition of a simple sentence aligns perfectly with the provided choice.