Here, we'd want x as the hypotenuse (as that is the longest part of a right triangle). So, 6 cm and 9 cm would be the legs.
Using the Pythagorean theorem, we can find the value of x:
62 + 92 = x2
36 + 81 = x2
117 = x2
x = √117, so I'd think that would fall under E) Other. :D