Please choose the correct answer to the question: A pod of dolphins is swimming while searching for food. The youngest dolphin swims away from the pod and is lost. The rest of the pod searches for the young dolphin by clicking into the water. The young dolphin is found because of

Answer1: echoes from noise Answer2: vibrations from drums Answer3: sound of water Answer4: movement in air

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