Duplicate gene, supplementary gene and polymorphic gene can be grouped under:
Gene interaction
Linkage
Recombination
Maternal effect
As discussed in the Interaction of Genes - Allelic and Non-allelic -
Gene interaction can be defined as a phenomenon of two or more genes affecting the expression of each other in various ways in the development of a single character of an organism. The following types of gene interactions that can be studied are Dominant epistasis, Supplementary gene interaction, Complementary factor, Polymorphic gene and Duplicate gene action.
Hence, the correct option is (a).