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 for normal antennae (a) is recessive to the allele for mutated antennae (A).
A certain fruit fly from this group has the heterozygous genotype Aa for the antenna type gene.
Based on this information, what is this fly's phenotype for the antenna type trait?
A. mutated antennae
B. normal antennae
Determine the correct option from the provided choices and reply with its corresponding letter.

A