Record your prediction (hypothesis) as an "if then" statement. (for example: if you select the go button, then the train will move)
if  the sound source is moving  then the pitch of the sound will to the observer.

Consider a production line with five stations. station 1 can produce a unit in 9 minutes. station 2 can produce a unit in 10 minutes. station 3 has two identical machines, each of which can process a unit in 12 minutes (each unit only needs to be processed on one of the two machines. station 4 can produce a unit in 5 minutes. station 5 can produce a unit in 8 minutes. which station is the bottleneck station?