Final answer:
The sexual phenotype of the fruit fly is female.
Step-by-step explanation:
The sexual phenotype of a fruit fly with two sets of autosomes, 1 X chromosome, and no Y chromosome is female. In fruit flies, females have two X chromosomes (XX) and males have one X chromosome and one Y chromosome (XY). Since the fruit fly in question has only 1 X chromosome and no Y chromosome, it can only be female.