The correct answer is option B. Genotype AA, phenotype-Unaffected.
The cystic fibrosis is a condition caused by the inheritance of the two recessive allele, It is an autosomal recessive disease.
In the given case, the parents are carriers, and the carriers are always heterozygotes. Hence, the phenotype of the both parent should be Aa. A possible cross of the parents is shown in the figure below.
In case, the progeny have a single dominant trait, the child would not be affected, but will be a carrier and can pass the disease to offspring. In case, the child inherit both the dominant allele (homozygous dominant) from the parents, then he/she would be unaffected. In case, the phenotype of the child is homozygous recessive then it would be affected.
