Context: This passage describes the cystic fibrosis trait in humans:

In a group of humans, some individuals have cystic fibrosis and others do not. In this group, the gene for the cystic fibrosis trait has two alleles. The allele F is for not having cystic fibrosis, and the allele f is for having cystic fibrosis.
Darnell, a human from this group, has cystic fibrosis. Darnell has two alleles for having cystic fibrosis.
Based on this information, what is Darnell's phenotype for the cystic fibrosis trait?
A. ff
B. having cystic fibrosis
Select the correct answer from the given choices and respond with the letter of the chosen option.
Answer: B