How many different ways can 3 cubes be painted if each cube is painted ... ...

How many different ways can 3 cubes be painted if each cube is painted one color and only the 3 colors red, blue, and green are available? (Order is not considered, for example, green, green, blue is considered the same as green, blue, green.)
(A)    2
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Nova Math - Problem Set M: Elimination Strategies