The correct option is C Polymorphism
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species - in other words, the occurrence of more than one form or morph. All the common blood types, such as ABO blood group system, are genetic polymorphisms. There are more than two morphs: the phenotypes A, B, AB and O are present in all human populations, but vary in proportion in different parts of the world. The phenotypes are controlled by multiple alleles at one locus.