The correct option is C 8 cm
Total surface area of a cuboid is given by 2(lb + lh + bh)
where l, b and h represent length, breadth and height of the cuboid repectively.
Since area is equal to 208 cm2
2(lb + lh + bh) = 208
lb + lh + bh = 104
4l + 6l + 24 = 104
10l = 80
l = 8 cm