7. Which of the following is true in the condition of a parallelogram, "a diagonal divides a parallelogram into two congruent triangles"?
a. In quadrilateral JACK, ∆AJKA = ∆CAK. Therefore, JACK is a parallelogram.
b. In quadrilateral JESZ, <J = <E and <E = <Z. Therefore, JESZ is a parallelogram.
c. In quadrilateral EDNA, ED || AN and EA II DN, ED = AN and EA= DN. Therefore, EDNA is a parallelogram.
d. In quadrilateral ERIC, m< E + m< R = 180°, m<R+ m< N = 180°, m<N + m<C = 180°, m<E + m<C = 180°. Therefore, ERIC is a parallelogram.​