Context: This passage describes the antenna type trait in fruit flies:

In a group of fruit flies, some individuals have mutated antennae and others have normal antennae. In this group, the gene for the antenna type trait has two alleles. The allele A is for mutated antennae, and the allele a is for normal antennae.
A certain fruit fly from this group has mutated antennae. This fly has one allele for mutated antennae and one allele for normal antennae.
Based on this information, what is this fruit fly's phenotype for the antenna type trait?
A. Aa
B. mutated antennae
Pick the correct answer from the listed options and provide the letter of the selected option.
Answer: B