A healthy young couple are both carriers of cystic fibrosis; the chance that each of their future children will inherit this serious illness is

A) More information is needed about the couple's parents and grandparents to determine probability.
B) 25%.
C) 0%, because cystic fibrosis is not an inherited illness.
D) 50%.
E) 100%, because both parents are identified as carriers of cystic fibrosis.