What is friction? A. f net= ma B. the normal force C. the wearing down of surfaces D. forces opposing the motion of surfaces in contact with each other

D. Forces opposing the motion of surfaces in contact with each other

Explanation:

Friction moves in the opposite direction of the object.

it is the second option.

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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