A right triangle must satisfy this equation: a^2 + b^2 = c^2
a= shortest length
b=medium length
c=the longest length
a triangle with sides 4,5,6 will satisfy not this equation because:
4^2 + 5^2 ≠ 6^2
16+25 = 41
41 ≠ 36
so the answer is C.
Hope this helps.
-Jabba
