9) D
We first need to know the genotype of mouse 2.
We know mouse 1 is homozygous dominant, meaning it is CC.
The white mouse must then be homozygous recessive, cc.
C C
c Cc Cc
c Cc Cc
There is a 100% chance that mouse 2’s genotype is Cc.
If mouse 1 and mouse 2 breed, these could be the following genotypes of the offsprings:
C C
C CC CC
c Cc Cc
The offsprings could either be homozygous or heterozygous.
Percentage heterozygous = 50%
Since ‘C’ is the dominant allele and all genotypes contain the C allele. Therefore, all phenotypes would be black only.
So we have 50% heterozygous, black only phenotype and homozygous and heterozygous genotypes. this only corresponds to row D in the question table.