Doppler effect ambiguity

The setup is ambiguous regarding whether the observer moves with the car or is stationary in the lab frame.

Steps:

• Identify the source as stationary at Q emitting frequency f.
• Note the car moves at constant speed toward Q along straight line PQ.
• Parse "stationary observer at point O attached to the car" as unclear: "stationary" could mean lab frame (fixed, hears f constant) or relative to car (moving toward source, hears >f constant).
• Conclude Doppler shift depends on observer motion, but phrasing prevents determining relative velocity.

Not enough information to select an option.

Final answer: Not enough information.