When the sheet in fig. (X ) is folded to form a cube, then ‘F ’ appears opposite ‘C’ and ‘A’ appears opposite ‘D'. Therefore, the cube in fig. (A ) which shows ‘F ’ adjacent to ‘B ’, the cube in fig.(C ) which shows ‘E’ adjacent to ‘ C’ and the cube in fig. (D) which shows ‘A’ adjacent to ‘D ’ cannot be formed.