gas is a kind of substance & a liquid is a kind of substance & a solid is a kind of substance & substances are made of matter ->  gas, liquids, and solids are made of matter  gas, liquids, and solids are made of matter & waves can travel through matter ->  waves can travel through gas, liquids, and solids  waves can travel through gas, liquids, and solids & longitudinal wave is a kind of mechanical wave -> longitudinal waves can travel through gas, liquids, and solids