DEF is a right traingle if the three sides are 24 40 and 17

If it is, then the squares of the short side and the medium side add up to the square of the longest side.

Let's check it out:

Square of the short side = 17² = 289

Square of the medium side = 24² = 576

These two squares add up to (289 + 576) = 865

Square of the longest side = 40² = 1,600

865 is not equal to 1,600.

So these three numbers do not make a right triangle.

i believe the answer is the polygon, heptagon.