Which complex sentence is punctuated correctly? When your favorite song comes on let me know. Charlotte met us, before she went home. If you need a ride home, Julian will be driving.

When it comes to complex sentences, if a dependent clause comes before an independent one, there has to be a comma between them. Having that in mind, the correct answer is the final option - If you need a ride home, Julian will be driving.

In the first sentence, there should be a comma between those two clauses. In the second one, there shouldn't because the dependent clause comes second.