A phenotypic ratio of 9:4:3 is indicative of epistasis. It is referred to as recessive epistasis. It is a phenomena where one gene pair expression deoends on the other gene pair.
Multiple alleles influence the same trait which are considered as the alternative of similar gene. Polygenic inheritance is about a trait of more than one gene. Codominance happens when two alleles of similar gene are being expressed separately to produce various traits in an individual.
Answer - D. Epistasis
