A compound sentence is made up of two or more simple sentences joined with a conjunction.
Complex sentences must include at least one dependent clause introduced by a subordinating conjunction or a relative pronoun and an independent clause.
A compound-complex sentence has one complex sentence joined to a simple sentence with a conjunction.
Therefore, the sentence, "because our favorite restaurant was closed, we decided to cook dinner at home." is a complex sentence. This is the correct answer because the dependent clause, "because our favorite restaurant was closed" was introduced by the subordinating conjunction, "because". It also has an independent clause, "we decided to cook dinner at home."
