The correct answer is A. Magnetostriction.
Magnetostriction is the property of some materials to change their shape when they are placed in a magnetic field. This change in shape can cause the material to vibrate, which can produce a noise. The noise is typically a low-pitched hum, but it can also be a higher-pitched squeal.
Magnetostriction is a common problem in electrical transformers and motors. The vibrations can cause the transformer or motor to overheat, and they can also cause noise pollution. To reduce magnetostriction, manufacturers use materials that are less susceptible to the effect, or they design the transformers or motors in a way that minimizes the vibrations.
Boo, hum, and zoom are not terms that are used to describe the noise resulting from magnetostriction.