Answer:
C. I want to sleep, but he wants to go outside
Step-by-step explanation:
A compound sentence is a sentence that has at least two independent clauses joined by a comma, semicolon, or conjunction. An independent clause is a clause that has a subject and verb and forms a complete thought. If you were to separate sentence option C., you are able to see that it contains two independent clauses that make sense by themselves.
I want to sleep. and He wants to go outside.
These independent clauses are joined by a comma and a conjunction (the word "but").