D. 100 square inches Step-by-step explanation:
As you know, a cube has 6 faces, and each face is a square, and the 6 faces are equal.
then, the total surface area of the cube is equal to 6 times the surface area of one of the faces:
6*f = 600 in^2
then the surface area of one face is:
f = (600/6) in^2 = 100 in^2
Then the correct option is D
