Atul is the son of Zamir. Alka is the daughter of Aman. Sheela is the wife of Aman. Mohan is the son of…

The correct choice is: “Sister”

Aman and Sheela are husband and wife. Alka is Aman’s daughter and Mohan is Sheela’s son, so Alka and Mohan are children of the same couple: Alka is Mohan’s sister. Alka is female, so “Uncle”, “Son” and “Father” cannot describe her. The statement about Atul and Zamir is irrelevant.