The correct option is C Bateson
Epistasis is a phenomenon that consists of the effect of one gene being dependent on the presence of one or more 'modifier genes' (genetic background). Similarly, epistatic mutations have different effects in combination than individually.
The genes of an individual do not operate isolated from one another but are functioning in a common cellular environment. Thus, it is expected interactions between genes would occur. Bateson and Punnett performed a classical experiment that demonstrated genetic interactions. They analyzed the three comb types of chicken known to exist at that time. This observation suggests that two genes may control the phenotype of the comb. The gene interactions and genotypes were determined by performing the appropriate test crosses. Thus, the correct answer is option C.