Context: This passage describes the Marfan syndrome trait in humans:

In a group of humans, some individuals have Marfan syndrome and others do not. In this group, the gene for the Marfan syndrome trait has two alleles. The allele for having Marfan syndrome (M) is dominant over the allele for not having Marfan syndrome (m).
Roy is a human from this group. Roy has the homozygous genotype mm for the Marfan syndrome gene.
Based on this information, what is Roy's phenotype for the Marfan syndrome trait?
A. having Marfan syndrome
B. not having Marfan syndrome
Determine the correct option from the provided choices and reply with its corresponding letter.

B