A cube is made by folding the given sheet. In the cube so formed, what would be the letter on the opposite side of the letter A?

As we know that the -

alternate surfaces are opposite to each other.
No two opposite surfaces are touched by side or by corners
So, by using the above rule we can find the opposite surface of open dice;
Below are the opposite surfaces;

When folded into a cube, "A" and "C" are not adjacent; therefore, they could be opposite each other.

Similarly, "B" and "D" do not touch, so they can be opposite.
"F" and "E" are on opposite sides based on their positions in the net.
Following this arrangement:
The letter on the opposite side of "A" is C. ​​