A Sonic Boom Can Be Heard by a Listener

Multiple Choice

A sonic boom can be heard by a listener

A) only at (or in the vicinity of) the time when the speed of the object reaches the speed of sound in the medium.
B) The previous answer is basically correct but must be modified to account for the time it takes the sound to reach the listener.
C) whenever the speed of the object is greater than or equal to the speed of sound in the medium.
D) The previous answer is basically correct but must be qualified by stipulating that the listener be at a location where the shock wave passes.