Which labels are correct for the regions marked? X: Slower in gases than liquids Y: Faster in solids than gases Z: Velocity depends on medium X: Faster in gases than liquids Y: Slowest in solids Z: Faster in liquids than gases X: Slower in solids than liquids Y: Velocity depends on medium Z: Faster in liquids than gases X: Velocity depends on medium Y: Fastest in gases Z: Slower in liquids than solids