Diana is exploring caves on her field trip. She enters a cave and shouts out aloud. She immediately hears the echo of her own voice. What is the most likely reason for the echo?

Students design a model roller-coaster track. they place a rubber ball at the highest point on the track and let it go. the ball rolls along the track pulled only by the force of gravity. eventually, it comes to a stop. which change to the design will result in the ball moving the greatest distance?