The Face-Centered Cubic Unit Cell to the Right Has Been

Multiple Choice

The face-centered cubic unit cell to the right has been shaded to add clarity; the balls in the corners are black: those in the faces are gray. If the corners of the unit cells are at the center of the corner spheres, how many atoms are in one unit cell?

A) 1
B) 2
C) 3
D) 4
E) 6