In the case of complementary activities of the dominant alleles of two genes, after the crossing of two heterozygous organisms (of the AaBb genotypes) the following outcome is expected:
A. only one phenotype
B. three phenotypes in the ratio 1:2:1
C. two phenotypes in the ratio 9:7
D. two phenotypes in the ratio 15: 1
E. four phenotypes in the ratio 9:3:3:1