Pretend human eye color is determined by a single gene, with brown eyes (B) being dominant over blue (b). A brown-eyed man marries a blue-eyed woman, and they have three children. Two of the children are brown-eyed, and one is blue-eyed. What is the probability their fourth child will have the genotype Bb? (2 points)
A. 100%
B. 75%
C. 50%
D. 25%