Concept:Colour blindness is an X-linked recessive trait, so a son’s X chromosome always comes from his mother.
Explanation:A colour blind woman has the genotype
XcXc, while a normal man has the genotype
XCY.
A son receives the Y chromosome from his father and the X chromosome from his mother.
Since the mother carries only the recessive colour blind allele
Xc, every son she has must inherit this X chromosome.
Therefore, all sons will be colour blind, giving a probability of
100%.
Answer:B.
100%