A colourblind girl is rare and can be born when

Options

A. Her father is colourblind and mother has normal vision but her mother's father (maternal grandfather) is colourblind
B. Her mother is colourblind, even if father has normal vision
C. Even when both her parents have normal visioon provided the grand parents were colourblind
D. Her mother is colourblind and her father had normal vision but her paternal grandfather (father's father was colourblind)

Answer

A