Answer: hello your question is incomplete below is the missing part 
What is Azimuth ?
answer : angle of a sound source on the horizontal plane relative to a point in the center of the head between the ears ( D ) 
Step-by-step explanation:
Azimuth is the described as angle of a sound source ( between the North ) and it is measured in a clockwise direction in relation to the observer ( Human ear ) 
Hence the option that fits in is : angle of a sound source on the horizontal plane relative to a point in the center of the head between the ears