How is it possible for someone to put an ear to a wall and hear someone in the next room? a. sound waves can travel though solids. b. the waves travel from room to room via air. c. there must be some air in the wall so the sound can travel through it. d. sound waves change to electromagnetic waves and then back again.

The answer is A. Sound can travel through matter (solids, liquids, and gases). Sound travels faster in solids, then slower in liquids and slowest in the air. When the person in the next room makes noise, the sound travels through the air in their room, through the solid wall and in the air in your room and into your ear.

they are known to reach a speed of 21 miles per hour