Which set of lengths cannot form a right triangle? a 20 mm, 48 mm, 52 mm b 10 mm, 24 mm, 26 mm c 11 mm, 24 mm, 26 mm d 5 mm, 12 mm, 13 mm?

All of the sets of numbers have the ratio 5:12:13 except selection C, which cannot form a right triangle.