PLEASE HELP!!! The ball moves along a flat surface. Then it moves forward down a hill, and then
finally stops.
The ball doesn't move at first. Then it moves forward down a hill and finally stops.
The ball is moving at constant velocity. Then it slows down and stops.
The ball doesn't move at first. Then it moves backwards and then finally stops.
The ball moves along a flat area, moves backwards down a hill and then it keeps
moving

layer a is the exosphere and layer b is the thermosphere.   is the answer i think but i hope this .

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

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form