Correct option (d) 0. 25
Explanation
When a colourblind man (XCY) marries to a woman with normal sight (XX) who has no family history of colour blindness, all of their sons will be normal pure and all of their daughters will be carriers as shown below
So in the next generation, the children of all of their son will be normal in all conditions (except the case in which the wife involved is not carrier neither colourblind). For carrier daughters.
(i) If they many to a normal man 50% of their grandsons will become colourblind as
(ii) If carrier daughter marries to a colourblind man 50% of their grandson will be colourblind along with 50% of the gland daughter while rest 50% of the grand daughters will be carriers as
So in both the above cases the result shows 50% of grand sons will be colourblind which in terms of over all progenies (son + daughters) comes as 25% thus confirming tire probability as 0.25.