Three positions of the same cube are shown; its faces carry the letters G, H, J, K, M and N. Which two letters are on opposite faces?

G is seen next to J, M, N and K, so G is opposite H. J is seen next to G, M, H and K, so J is opposite the remaining letter N, and K is opposite M. M–J, G–K and H–N are all seen side by side, so none of them can be opposite.