You are standing on a street corner and you hear an ambulance siren. The
pitch of the siren seems to be getting higher. What do you expect will happen
next?
A. The siren will get louder and higher as the ambulance moves
toward you.
OB. The pitch of the siren will continue to get higher, but you will not
see the ambulance because it is moving away.
C. The pitch of the siren will change unpredictably as it approaches
you.
OD. The siren will eventually fade as the ambulance moves away from
you.