Two trains are blowing their whistles. The first train is stationary, and the
second one is moving toward Tom. If the two whistles are identical, how do
the two whistles sound tb Tom?
O
A. The stationary whistle has a lower pitch.
B. Both whistles have the same pitch.
C. The stationary whistle starts lower and ends higher.
O
D. The moving whistle has a lower pitch.