The length of the hypotenuse in a triangle is the longest side opposite the largest angle. In this case, the angles given are 62 degrees and 28 degrees. Therefore, the angle opposite side \( o \) (which is 13 units and potentially the largest angle, given that the angle sum of a triangle is 180 degrees) is the largest, making side \( o \) the hypotenuse.
Thus, the correct response is:
The length is 13 units because the hypotenuse is the longest side.