Pointing to a photograph, a person said, “His mother is the wife of my father’s only son”. How is the speaker related to the person in the photograph?
The statement given is: "His mother is the wife of my father’s only son."
Putting it together, "His mother is the wife of my father’s only son" means "The mother of the person in the photograph is married to my father's only son ."
If the mother of the person in the photograph is married to the speaker, then the person in the photograph is the speaker's brother. Therefore, the speaker, being the brother's sister, is indeed the aunt of the person in the photograph.
Option C) is correct.