Context: In a group of rose plants, some individuals have thorns and others do not. In this group, the gene for the thorns trait has two alleles. The allele R is for having thorns, and the allele r is for not having thorns.
A certain rose plant from this group has thorns. This plant has two alleles for having thorns.
Based on this information, what is this rose plant's phenotype for the thorns trait?
A. RR
B. having thorns
Select the correct answer from the provided options and reply with the letter associated with it.

B