Tongue rolling is a dominant trait. Arun who cannot roll his tongue, marries a woman who is a carrier of the trait. What percentage of their children can roll…

50%

Reason — Arun cannot roll his tongue, so he is homozygous recessive (tt). His wife is a carrier, so she is heterozygous (Tt). The cross tt × Tt gives 50% Tt children, who can roll their tongue, and 50% tt children, who cannot.