The correct answer is A. Incomplete dominance
Explanation:
Incomplete dominance occurs in genetics when two alleles lead to a new observable trait (phenotype), this occurs because the two alleles (variants of genes) combine or express at the same time, and therefore neither of the alleles shows a complete dominance. This type of dominance differs from codominance because in codominance both alleles express equally without combining or creating a new phenotype.
The case presented is an example of incomplete dominance because the allele that leads to black coat and the one that leads to white coat are combining, and therefore none of the alleles is completely dominating; also, in this case, there is a new phenotype or trait, which is the gray coat of the offspring that results from combining black coat and white coat alleles.
