The parents of a 3-month old infant with cystic fibrosis (CF) want to know how their child got this disease, because no one in either of their families has CF. What is the nurse's best response based on the understanding of CF?

A. Both parents are carriers of the CF gene: Cystic fibrosis follows an autosomal recessive inheritance pattern, meaning both parents must carry one copy of the defective gene, even if they do not have the disease themselves. The child inherits one copy of the defective gene from each parent to develop CF. B. The inheritance pattern is multifactorial: CF is not a multifactorial disease; it follows a clear recessive genetic inheritance pattern. C. The result is probably a genetic mutation: CF is caused by a genetic mutation, but this mutation is inherited from both parents. It is not usually a spontaneous mutation unless it occurs in the parental genetic material, which is rare. D. Only one parent carries the CF gene: For the child to inherit CF, both parents must be carriers of the gene. If only one parent carries the gene, the child would be a carrier, not affected by the disease.