A loud alarm attached to a metal fence begins to ring. Student X has her ear against a pole of the fence while student Y stands away from the fence, as shown below. Both students are the same distance from the alarm.
Which of the following statements explains what happens in this situation?

a. Student X hears the alarm first because sound travels faster in solids than in gases.

b. Student Y hears the alarm first because sound travels faster in gases than in solids.

c. Student X hears the alarm at a higher pitch because solids are denser than gases.

d. Student Y hears the alarm at a higher pitch because gases are denser than solids.