Veins returning to the heart can close to prevent the backflow of blood. which component in the veins contributes to this process?

the father in the first generation probably had the recessive colorblind trait in his x chromosome. if he and his wife both had the colorblind trait, even if she had 1 recessive and 1 dominant, then that trait would be passed on to their kids.

(since you didn't attach the family tree this is just an assumption)

answer; i believe the correct answer is (a)0