If the total sum of numbers on opposite faces of a cubical block is always 7, find the figure which is correct.

as per the question, sum of the numbers on opposite sides or faces is always 7. Therefore
1 appears opposite 6,
2 appears opposite 5 and
3 must appears opposite of 4.
In (a) 1 cannot adjacent to 6 In (b) 3 cannot adjacent to 4 In (d) 2 cannot appears adjacent to 5 Hence only option (c) is correct.
For the better understanding take a dice and apply the same steps which is mentioned above.