How can a megaphone used by a cheerleader allow people on the opposite side of a field to hear her better? a) the metal or plastic of the megaphone cannot absorb the sound waves. b) the inside of the megaphone is like a vacuum because its shape eliminates air pressure. c) the air pressure is greater inside the megaphone than outside and the sound waves are able to travel further. d) solid objects can change the direction of sound waves; megaphones allow users to determine the general direction of the sound.