Sound waves traveled slowly down the canyon. Sound waves were absorbed by the canyon wall. Sound waves reflected off the canyon wall. Sound waves were refracted around the canyon.
I gave my students this multiple choice question: Campers shouted toward a canyon wall. What characteristic of sound best explains why the campers heard an echo?

Only one answer is correct among these 4 choices:
- Sound waves traveled slowly down the canyon.
- Sound waves were absorbed by the canyon wall.
- Sound waves reflected off the canyon wall.
- Sound waves were refracted around the canyon.

Could you tell me which one is correct?

Sound waves reflected off the canyon wall.