I believe the answer is B. As the scene opens, a dim light shines on the stage, and the main characters are arguing.
Explanation:
compound-complex sentences have to have two or more coordinate independent clauses and one or more dependent clauses. In this case, the independent clause would be "As the scene opens, a dim light shines on the stage", because this by itself could still make a complete and coherent sentence. The dependent clause is "the main characters are arguing", since this phrase alone cannot be considered a complete sentence and it <em>depends</em> on the other phrase in the sentence to be comprehensible.
