Answer:
I think it's a because it's not dry not windblown.
Answer: The dependent clause follows the independent clause in this sentence, so no comma is needed.
Explanation:
When a dependent clause follows an independent clause, there is not need to include a comma as opposed to when the dependent clause is before the independent clause.
In this case the dependent clause being<em> "because her brother’s stereo was turned up to full volume"</em>, follows after the independent clause which is, <em>"Beatrice was unable to concentrate on her project"</em>. There is therefore no need to put a comma.
“At that point, the song siren captured them and they became addicted.”