Context: This passage describes the sickle-cell disease trait in humans:

In a group of humans, some individuals have sickle-cell disease and others do not. In this group, the gene for the sickle-cell disease trait has two alleles. The allele A is for not having sickle-cell disease, and the allele a is for having sickle-cell disease.
Trisha, a human from this group, has sickle-cell disease. Trisha has two alleles for having sickle-cell disease.
Based on this information, what is Trisha's genotype for the sickle-cell disease gene?
A. having sickle-cell disease
B. aa
From the given choices, choose the correct answer and respond with the letter of that choice.
Answer: B