Question

As observed in labrador retriever coat colors in recessive epistasis, b locus regulates pigment production while e locus regulates pigment deposition to hair shaft. which gene is hypostatic?

Answer 1

If your choices are the following (see attachment), then the answer is E gene.
It is stated that hypostatic gene is one whose phenotype is altered by the expression of an allele at a separate locus, in an epistasis event. So the allele altering the espistatis event is the E gene.