Two Characters That Appear in a 9:3:3:1 Ratio in the F₂

Two characters that appear in a 9:3:3:1 ratio in the F₂ generation should have which of the following properties?

A) Each of the traits is controlled by single genes.
B) The genes controlling the characters obey the law of independent assortment.
C) Each of the genes controlling the characters has two alleles.
D) Four genes are involved.
E) Sixteen different phenotypes are possible.