If a man who is colour blind marries a women, who is pure normal for colour vision, the chances of their sons have colour blindness is

Colour blindness is found more in males than in females because

In pedigree analysis, the square, blackened and horizontal lines represents

Given below is a pedigree chart showing the inheritance of a certain sex- linked trait in humans.

The trait traced in the above pedigree chart is

A couple whose sons are colourblind with $AB$ blood group, identify the parents from the following..