Frida Is Sitting on a Park Bench When She Hears

Frida is sitting on a park bench when she hears a police car turn on its siren. Although she cannot see the police car, she is certain that it is nearby. What cue did her brain most likely use to come to this conclusion?

A) the slight energy difference between each ear
B) the slight time difference between when the sound reached each ear
C) the overall loudness of the sound
D) the frequency of the sound