5) E

On the conventional die, the face opposite to 2 would be 5 (2 + 5 = 7).

We can conclude that the black die is conventional. The orientation of 6 compared to 4 and 3 shows that 4 and 3 are on opposite sides. Since 4 + 3 = 7, the black die must be conventional.

On the white die, the orientation of 6 compared to 4 and 5 shows that 4 and 5 are on opposite sides.

The faces around 6 are 5, 3, 4 and 1. The face opposite 6 must be the only remaining number: 2.

So 2 is opposite 6.