The correct answers are the following:
1. Complex sentence. It has a dependent clause joined to an independent clause. The independent clause is "The case club is holding a dance" and the dependent clause is "which is a community service group".
2. Compound sentence. It has two independent clauses joined by the coordinating conjunction "and". The two independent clauses are "Heather is in charge of decorations" and "Enrique is bringing snacks".
3. Simple sentence. It has an independent clause which is "The senior class took a trip to Washington, D.C. and Annoplis for their research project".
A compound-complex sentence has two independent clauses joined to one or more dependent clauses.
