Newton's third law can be summarized as "every action has an equal and opposite reaction". In this problem, consider the action of the entire Earth on a person standing at rest on the ground and the opposite reaction, where ‘action’ and ‘reaction’ are understood to mean ‘force’ and ‘reaction force’

What is the "equal and opposite reaction force to the gravitational force of the Earth acting on the person?

(1) The contact force of the ground on the person, keeping them from traveling towards the center of the Earth.
(2) Since the person is not moving, there is no reaction force in this situation.
(3) The mutual gravitational interaction between the Earth and the person.
(4) The gravitational force, exerted by the person on the Earth.

layers of the earth affect the waves and these effects are seen on instruiments such as seimometers

a. are

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