Which option correctly identifies a compound sentence?

A compound sentence is defined as a sentence that contains at least two independent clauses connected by a coordinating conjunction, such as "and," "but," or "or." In the correct option, "She was tired, but she finished her work," there are two independent clauses: "She was tired" and "she finished her work." Each clause can stand alone as a complete sentence, and they are joined by the coordinating conjunction "but," which illustrates a contrast between the two ideas.

This structure is what distinguishes a compound sentence from the other options. The first choice expresses a compound action but lacks independence in its clauses. The third choice is a complex sentence, which includes a dependent clause introduced by "even though." The fourth option is a simple sentence, presenting a single action without any conjunctions or additional clauses. The clarity of the two independent clauses connected by a conjunction is what makes the second option a compound sentence.