Final answer:
The sentence in question is a compound sentence because it contains two independent clauses joined by a conjunction. It lacks a dependent clause, which rules out the complex and compound-complex options. The correct option is B.
Step-by-step explanation:
The sentence \"I watched the movie last night, but I didn't like it.\" is an example of a compound sentence. A compound sentence consists of two or more independent clauses (which can stand alone as separate sentences) joined by a conjunction such as \"and\", \"or\", or \"but\". The sentence mentioned contains two independent clauses, \"I watched the movie last night\" and \"I didn't like it\", which are joined by the conjunction \"but\". Therefore, the correct answer to the question is B) compound.
Each of these clauses has its own subject and predicate, making it able to stand on its own. The sentence does not contain a subordinate clause, which is necessary for complex and compound-complex sentences. Complex sentences have at least one dependent (or subordinate) clause that cannot stand alone, while compound-complex sentences mix the elements of compound sentences with the elements of complex sentences.