I'm going to go with complex.
Complex sentences has an independent clause and a dependent clause. Your independent clause is: Teresa brought us paper plates. Dependent clause would be For our sandwiches.
For a compound sentence to occur you would need two clauses to be joined together as one sentence. Usually one of the indications to a compound sentence is if there are either a semicolon, colon, a conjunction (...,and) with a comma, a dash mark (ie -), a conjunction with a semicolon (...; but). Compound sentences have two or more independent clauses. complex sentence can have one or more dependent clauses (meaning they cannot stand alone.... more information is needed for the sentence to be complete and not sound like a fragment) and one independent clause (can stand alone... no more information is needed. The sentence is complete...not a fragment).
Simple sentence has one independent clause. It is a complete sentence.
Hopefully this helped and good luck
