A person places one ear on a steel railway track and the other in the air. She hears the sound of an approaching train first through the rail. Which option best explains this observation?
(a) Sound travels faster in steel because its density is lower than that of air.
(b) Sound travels faster in steel because the steel track amplifies the vibrations, making them reach earlier.
(c) Sound travels faster in steel because steel is much more elastic than air.
(d) Sound travels faster in steel because the steel rail is warmer than the surrounding air.