|A) sister of father-in-law||B) sister|
|C) mother||D) mother-in-law|
Brother of person's wife → brother-in-law of the person. Hence, the son of lady's brother is brother-in-law of the person.
Therefore, the brother of the lady is the father-in-law of the person. Hence, the lady is the sister of the person's father-in-law.