What is an example of a complex sentence?

A complex sentence is defined as a sentence that contains at least one independent clause and at least one dependent clause. This structure allows for the expression of more nuanced ideas and the inclusion of additional information about the main action.

The example provided in the correct answer, "Although it was raining, we went for a walk," illustrates this perfectly. Here, "Although it was raining" serves as the dependent clause, which cannot stand alone as a complete thought. It provides additional context for the main action expressed in the independent clause, "we went for a walk," which does convey a complete idea. This combination showcases the relationship between the two clauses, indicating that the action of walking occurred despite the rain, thereby adding complexity to the sentence.

The other examples presented do not fulfill the criteria for complex sentences. They may be complete sentences or compound sentences, but they lack the necessary combination of independent and dependent clauses that characterize a complex sentence.