Answer:
The correct option is D) The mouse must be ff.
Step-by-step explanation:
A dominant trait arises due to a dominant allele. A dominant allele can be described as the allele which masks the effect of a recessive allele. A recessive allele can be described as the allele which gets suppressed by the dominant allele. For a dominant trait to occur, the genotype may be homozygous dominant or heterozygous. For a recessive trait to occur, the genotype must me homozygous recessive.
White mouse is recessive over the dominant brown mouse. Hence, for white colour to occur the alleles for the trait have to be homozygous.