Answer:
Your answer would be that the adverb phrase because of the siren modifies the word awakens.
Step-by-step explanation:
The sentence above contains an adverb clause, because of the siren. Adverb clauses, also called adverbial clauses, are dependent clauses that function as adverbs. As they are dependent clauses, they must have a subordinating conjunction to connect them to the rest of the sentence.
In this case, the subordinating conjunction introducing the adverbial clause is because. This adverbial clause is adding information as regards reason and it modifies the word awakens. It describes why the entire household quickly got up.