Well, you can always cut out papers of that shape and fold them...

The answer is 1

First one won’t make the cut, if you actually fold the paper carefully.

Malavika,

how to identify opposite faces if you are not able to do cut-outs (like in the exam hall!) ...

Rule 1. if you have 3 squares in a row or column, the 2 opposite squares will be separated by exactly 1 square in between.

Rule 2. opposite squares can NEVER share common edges or corners.

for the given diagrams ......

(1) using rule 1, we identify the opposite faces as 3-5, 4-2 and 6-1.

(2) using rule 1, we identify 5-2 as one pair.
next, consider square 3 and apply rule 2.
3 cannot be opposite to 1 or 6 because they share common corners, so 3 must pair with 4.
that leaves 1 to pair with 6.

(3) using rule 1, we identify 3-4 as one pair.
next, consider square 1 and apply rule 2.
1 cannot be opposite to 2 or 6 because they share common corners, so 1 must pair with 5.
that leaves 2 to pair with 6.

(4) using rule 1, we identify 3-5 and 1-2 as pairs.
that leaves 4 to pair with 6.

correct answer is (2) because only in (2) the pairs all add up to 7.