Genetics

Ajay and Vijay are siblings. Ajay can roll his tongue while Vijay cannot. What is the genotype of their
parents?
(a) Both the parents are homozygous dominant.
(b) Both the parents are homozygous recessive.
(c) One parent is homozygous dominant, and the other is homozygous recessive.
(d) Both the parents are heterozygous dominant.