Here are the coordinates for eight points on the coordinate plane (q > p > 0): A (0, 0), B (p, 0), C (q, 0), D (p + q, 0), E (0, q), F (p, q), G (q, q), and H (p + q, q). Which four points, if any, are on the vertices of a parallelogram?

a.
E, F, B, and D
c.
E, G, C, and D
b.
A, C, H, and F
d.
A, F, D, and G