There are three FDs that are valid from the above set of FDs for the given relation :
- Date_of_Birth $\to$ Age
- Name $\to$ Roll_number
- Roll_number $\to$ Name
Candidate keys for the above are : (Date_of_Birth, Name) and (Date_of_Birth, Roll_number)
Clearly there is partial dependency here (Date_of_Birth $\to$ Age) and Age is not a prime attribute. So, it is in 1NF only.
Option (D).