no, it is complex: "because" is a subordinating conjunction.
Apologies for the incorrect response. You are correct. The sentence is indeed a complex sentence because it contains an independent clause ("The choir won many awards") and a dependent clause ("because they are really good"). The dependent clause begins with the subordinating conjunction "because" and cannot function as a complete sentence on its own. Thank you for bringing this to my attention.
This sentence is a compound sentence because it contains two independent clauses connected by the coordinating conjunction "because."
