Which of the following is a simple sentence?

A simple sentence consists of a single independent clause that contains a subject and a predicate, expressing a complete thought. The correct answer presents such a sentence, where "The woman in the elegant, gold evening gown and diamond-studded tiara" serves as the subject, and "looked out of place in the convenience store" acts as the predicate. Together, they form a complete thought indicating that a specific woman looked out of place at a particular location.

In contrast, the other options do not meet the criteria for a simple sentence. The first option lacks a complete predicate, leaving it as a phrase rather than a complete sentence. The second option also fails as it does not have a subject to express a full idea. The third option contains multiple clauses, making it a complex sentence that conveys more information than a simple sentence would. Each of these alternatives highlights the characteristics of more complicated sentence structures, as they either lack completeness or include additional clauses.