Subject: mathqa
Question: a cube is divided into 512 identical cubelets . each cut is made parallel to some surface of the cube . but before doing that , the cube is painted with green on one set of opposite faces , red on another set of opposite faces , and blue on the third set of opposite faces . how many cubelets are painted with exactly one colour ?
Option: 
A: 312
B: 264
C: 216
D: 324
Answer: C