When dna ladder's rungs are the same width, why do a-t and g-c form complementary base pairs according to chargaff's rule
a. the larger c pairs with the smaller a, and the larger g pairs with the smaller t.
b. the larger a pairs with the smaller g, and the larger t pairs with the smaller c.
c. the larger a pairs with the smaller t, and the larger g pairs with the smaller c.
d. the larger t pairs with the smaller a, and the larger c pairs with the smaller g.