Answer:
Option A, Mutation
Explanation:
Mutation can cause the variation in a defined genetic set of an organism there by producing allele of varied types. However an allele is a variant gene. For example
A male flower has following allele – WW (representing dominant white color flower)
A female flower has following allele – ww (representing recessive blue color flower)
If these two flower mutate either through natural processes or though the mating, new species of flower with a different and unique genotype (allele set) is formed
for example a grey color flower with unique allele set - Ww
Alleles are carried on chromosome which expresses certain trait, variation in genotype also brings variation in allele's trait expression.
Hence, option A is correct
