9 : 3 : 3 : 1.
Explanation
In a dihybrid cross, two genes are considered at the same time. The phenotypic ratio of a dihybrid cross is 9 : 3 : 3 : 1. This means that 9 out of 16 offspring will have the dominant phenotype for both genes, 3 out of 16 will have the dominant phenotype for one gene and the recessive phenotype for the other gene, 3 out of 16 will have the recessive phenotype for one gene and the dominant phenotype for the other gene, and 1 out of 16 will have the recessive phenotype for both genes.