The following table lists the speed of sound in various materials. Use this table to answer the question.
 Substance Speed (m/s)
 Glass 5,200
 Aluminum 5,100
 Iron 4,500
 Copper 3,500
 Salt water 1,530
 Fresh water 1,500
 Mercury 1,400
 Hydrogen at 0°C 1,284
 Ethyl Alcohol 1,125
 Helium at 0°C 965
 Air at 100°C 387
 Air at 0°C 331
 Oxygen at 0°C 316
 Sound travels fastest in _____.
 solids
 liquids
 cold gases
 warm gases