Of both normal parents, the chance of a male child becoming colourblind are

Q. Of both normal parents, the chance of a male child becoming colourblind are

A.            no

B.            possible only when all four grand parents had normal vision

C.            possible only when father’s mother was colourblind

D.            possible only when mother’s father was colourblind

Answer: possible only when mother’s father was colourblind