Please choose the correct answer to the question: Campers shouted toward a canyon wall. What characteristic of sound best explains why the campers heard an echo?

Answer1: Sound waves traveled slowly down the canyon. Answer2: Sound waves were absorbed by the canyon wall. Answer3: Sound waves reflected off the canyon wall. Answer4: Sound waves were refracted around the canyon.

Answer format: answer1/answer2/answer3/answer4
Answer: answer3