Both husband and wife have normal vision though their father were colour blind and mother did not have any gene for colour blindness .The probability of their daughter becoming colour blind is :

Options

A. 0.5
B. 0.75
C. 0.25
D. None of these

Answer

D

Explanation

The wife, in the given case will be carrier of the disease (father was colourblind) but the husband has normal vision (mother did not have gene for colour blindness)
Thus, the cross can be shown as