In Mice, Black Coat Color Is Dominant to White Coat

In mice, black coat color is dominant to white coat color. In the pedigree below, mice with a black coat are represented by darkened symbols, and those with white coats are shown as open symbols. What could you conclude regarding the genotype of mouse II- 3 if a testcross resulted in 5 mice with black coat color and 6 mice with white coat color?

A) The genotype of II- 3 must be homozygous dominant.
B) The genotype of II- 3 could be homozygous dominant or heterozygous.
C) The genotype of II- 3 must be homozygous recessive.
D) The genotype of II- 3 could be homozygous recessive or heterozygous.
E) The genotype of II- 3 must be heterozygous.