Answer is the second option by the way :)) !
We'll make the alleles: Cc.
C is a healthy parent, and c is the cystic fibrosis (recessive).
If you make a punnett square and the parents are both Cc (healthy), then you would get CC, Cc, Cc, and cc. That cc is a 25% chance that the offspring will have that, which means there is a 25% chance the child will have cystic fibrosis.
Two healthy parents can have a child with cystic fibrosis if both the parents have the dominant allele and recessive allele, if both the parents have heterozygous alleles.
