Answer with explanation:
It is given that, coordinates of Isosceles trapezoid J K L M are J(-b, c), K(b,c), L(a,0), and M(-a,0).
To Prove: The diagonals of an isosceles trapezoid are congruent.
Proof:
Distance formula , that is distance between two points in x y plane is given by

Where,
are coordinates of two points in the plane.
Length of Diagonal J L

Length of Diagonal K M

So, we can see that,
J L = KM

Hence,The diagonals of an isosceles trapezoid are congruent.
So ,

Option C