What is the difference between contact and action-at-a-distance forces?
A. Action-at-a-distance forces are stronger than contact forces.
B. Contact forces are stronger than action-at-a-distance forces.
C. Contact forces require objects to physically touch, while action-at-a-distance forces do not.
D Action-at-a-distance forces require objects to physically touch, while contact forces do not.

A

Contact forces are forces that require the actual contact (touching) of two pieces of matter. ... A field force is a force that works at a distance. No touching is required. Gravity is a good example of a field force, because it works whether or not an object is touching something or touching nothing at all.

answer and explanation;

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