A Couple Who Does Not Have Cystic Fibrosis but Are

Multiple Choice

A couple who does not have cystic fibrosis but are both heterozygous has already had three girls with cystic fibrosis, and are hoping to have a healthy child for their fourth. What are the chances that the fourth child will be a healthy male?

A) 0
B) 1/8
C) 1/4
D) 3/8
E) 1/2