Answer:
B. magnitude of displacement of a sound pressure wave.
Step-by-step explanation:
In physics, amplitude means the maximum displacement attained by a particle from a particular position. The particle could be a wave or an object. When such particle reaches its peak during displacement, we say such particle has attained its amplitude. An example of such particle is the sound wave.
The amplitude of a sound is a measure of the loudness of the sound. In other words, a higher amplitude means a louder sound and vice-versa.