Answer: C. Compound.
Step-by-step explanation: a simple sentence is a sentence that is formed only by one independent clause (a phrase that has complete meaning on its own), a complex sentence is formed by a independent clause and at least one dependent clause (a phrase that doesn't have complete meaning on its own), and a compound sentence is formed for at least two independent clauses, in this case "the room was full" and "i had no place to sit."