Answer:
yellow; epistasis.
Explanation:
Epistasis may be defined as the phenomena in which the physical constitution of the individual gets influenced by the presence or the absence of the different genes.
The different types of epistasis are dominant epistasis, recessive epistasis and duplicate epistasis. The dog has yellow fur as it shows the case of recessive epistasis in which the recessive gene modifies the expression of black fur pigmented gene.
Thus, the correct answer is option (b).