The Parents of a 3-Month-Old Infant with Cystic Fibrosis (CF)want

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.The nurse's response is based on the understanding that with CF:

A) only one parent carries the CF gene.
B) both parents are carriers of the CF gene.
C) the inheritance pattern is multifactorial.
D) the result is probably a genetic mutation.