Answer:
"As she laughed to herself" is a dependent clause, meaning it cannot stand alone. It needs to be added to an independent clause to be considered a sentence. By adding it to sentence 5, it modifies how Jenna reacted to the situation. There are two ways to add a dependent clause to an independent clause. When you add the dependent clause to the end of the independent clause, like the sentence in the correct answer choice, you do not need a comma to separate the clauses. The word "as" shows the separation in clauses. You can also put the dependent clause before the independent clause and separate them with a comma.