ROTATE the elements either in clockwise or ANTI clockwise direction, to get the opposite pairs.In the above TWO dice, the common element is 3.Now, we'll rotate the elements in clockwise direction.First dice - 3, 5, 2Second dice - 3, 1, 6Therefore, 3 is opposite to 4.5 is opposite to 1.2 is opposite to 6.Hence, 6 is CORRECT.