children will be colorblind

1. Red-green color blindness is an X-linked recessive disorder.  If Allison is heterozygous (a carrier), and her husband, Michael, is NOT colorblind. What is the chance that their male children will be colorblind? (Note: you are calculating the probability for their MALE children only, in other words if they have 1 male child, what is the probability that he will be born with the disease?)

    0%
    25% or 1/4
    50% or 2/4
    75% or 4/4
    100% or 4/4