The correct answer is C. Aunt.
Abhishek’s father has only one child, who is a daughter. This girl is the daughter of Abhishek’s father’s daughter. This makes the girl Abhishek’s niece, and Abhishek’s wife the girl’s aunt.
A daughter is a female child. A mother is a female parent. An aunt is a female relative of a person’s parent, usually the sister of one’s mother or father. A sister is a female sibling.
In this case, the girl is not Abhishek’s daughter, because Abhishek does not have any children. The girl is also not Abhishek’s mother, because Abhishek’s mother is not the girl’s mother. The girl is also not Abhishek’s sister, because Abhishek and the girl do not share the same parents. Therefore, the only possible relationship between Abhishek’s wife and the girl is that of aunt.