50% (Answer Choice 3)
Explanation:
One important thing to keep in mind when solving sex-linked Punnett Squares is that males can never be carriers, since they have one X and one Y chromsome. Thus, it is only possible for females to be carriers, because they have two X chromsomes. Because of this, before solving the problem, you already know that 50% or less of the offspring can be carriers, thus eliminating two answer choices right off the bat. Now, the only way to find out whether 25% or 50% of the offspring are carriers is to solve the Punnett Square. The two female genotypes resulting from the cross is and
. Since both offspring have only one allele for color-blindness, both are carriers, which means that the answer is 50%.