I'm which medium would sound travel faster? A) across a room B) in a swimming pool C) through outer space D) through a rail road track

The snoud wave travels through the particles thus the closer the particles are, the faster the sound travels. The particles are the closets in solids, not so much in liquids and even less in gases. There are no particles in the outer space, so sound does not travel there. It travels the fastest through the rail road tracks (solid), slower through the swimming pool (liquid) and slowest through the room (gas).