Main clauses express a complete thought and appear in sentences. compound complex compound-complex all of the above.

Main clauses express a complete thought and appear in compound, complex and compound-complex sentences. Therefore, the correct answer is all of the above. A compound sentence is made up of two independent clauses which are joined by a coordinating conjunction. A complex sentence is made up of an independent clause and a dependent clause which are joined by subordinating conjunction. A compound-complex sentence is made up of two or more independent clauses and one or more dependent clauses.