A computer accessory comes in red (R) , grey (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}