In the endangered African watchamakallit, the offspring of a true-breeding black parent and a true-breeding white parent are all gray. When the gray offspring are crossed among themselves, their offspring occur in a ratio of 1 black : 2 gray : 1 white. Upon close examination of the coats, each hair of a gray animal is gray. What is the mode of inheritance?
A) one gene pair with black dominant to white B) one gene pair with codominance C) one gene pair with incomplete dominance D) two gene pairs with recessive epistasis E) two gene pairs with duplicate genes