The diagram below shows a sound wave traveling from a mass of cold air into a mass of warm air.
Judging from the diagram, which of the following statements is true?
A.
Sound travels faster through cold air than through warm air.
B.
Sound travels faster through warm air than through cold air.
C.
Sound travels at the same speed through both cold and warm air.
D.
A sound wave's wavelength shortens when it travels from cold air into warm air.