Answer:
The air molecules in the compressions of the second wave are more dense, so the sound is louder.
Step-by-step explanation:
In a closed room, Noah and Nina are sitting 15 m apart.
As Noah says the same sentence twice, Nina does not hear the sound the first time but she does hear the sentence the second time.
This happens as the air molecules in the compressions of the second wave are more dense. As a result, the sound is louder.
The correct option is ''The air molecules in the compressions of the second wave are more dense, so the sound is louder''