Red-green colorblindness in humans is a sex-linked trait. If a woman with normal vision, whose father was colorblind, married a man whose mother was colorblind, what would be the probability of their first child being a colorblind girl?
(A) 0 percent
(B) 12.5 percent
(C) 25 percent
(D) 50 percent
(E) 100 percent
