Which statement is the contrapositive of the following conditional: If a triangle is isosceles, then it has 2 congruent sides.

a. If a triangle does not have 2 congruent sides, then it is not isosceles.
b. If a triangle is isosceles, then it does not have 2 congruent sides.
c. If a triangle has 2 congruent sides, then it is isosceles.
d. If a triangle is not isosceles, then it does not have 2 congruent sdies.