GRAMMAR ERROR- SINCE THE RULE HAS BEEN MODIFIED AS YOU CAN SEE BELOW .WHY MY ANSWER IS WRONG ???

First question: Ramesh and Rajiv are men (pronoun: his). Had it just said, "Dr. Melhotra, Dr. Mishra" -> we'd not know the gender.

Second question: "Neither of the students" -> could be a guy, could be a girl; as mentioned in the solution: "if you don't know the pronouns of the person being described..."