Epistasis effect in which the dihybrid cross AaBb `xx` AaBb resulting in the ratio 12 : 3 : 1 is due to:
A. interaction between two alleles of different loci
B. interaction between two alleles of the same locus
C. dominance of one allele on another allele of both loci
D. dominance of one allele on another allele of the same locus
