The answer is D. I can't figure out why? The human range is from 20 Hz to 20 kHz...

(C) 2 kHz

Explanation:

The normal hearing frequency range of a person has a minimum of about 20 Hz, which is the about the frequency of the lowest pipe organ pipe. The maximum frequency that a human can ear comfortably is 20 kHz

Therefore, the student will not be able to hear sounds less than 20 Hz, and sounds above 20 kHz and the student will only be able to hear the 2 kHz sound.

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

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