A computer accessory comes in red (R), gray (G), or black (B) and has an optical mouse (O), mechanical mouse (M), or trackball (T). What are all the different combinations available for the accessory?
A) {R, G, B}
B) {RO, GM, BT}
C) {R, G, B, O, M, T}
D) {RO, RM, RT, GO, GM, GT, BO, BM, BT}