If a dice has numbers 1 to 6 on its faces and face 1 is opposite to 6, 3 is opposite to 4, then what will be the number on the face opposite to the face showing '2'? ​​

Given: 

If a dice has numbers 1 to 6 on its faces and face 1 is opposite to 6, 3 is opposite to 4.

Solution:

1 is opposite 6.

3 is opposite 4.

That means the numbers left are 2 and 5.
So, 2 must be opposite 5.

Thus, correct option is (b).