Answer:
The correct answer is C. dd
Step-by-step explanation:
As the allele of the dark brown hair is denoted by a capital letter(D) and of light brown hair by small letter(d) therefore dark brown hair allele is a dominant allele and light brown hair allele is recessive allele.
As recessive allele can only be expressed in the phenotype when it is present in homozygous condition in the offspring therefore the genotype of the dog having light brown hair would be dd.
D d
D DD Dd
d Dd dd
Genotype DD and Dd will express dark brown hair as it has the dominant allele for dark brown hair.