ER and Relational model

Question 1
Both (i) and (ii) will fail
(i) will fail but (ii) will succeed
(i) will succeed but (ii) will fail
Both (i) and (ii) will succeed
       Database Management System       ER and Relational model       Gate 2004-IT
Question 1 Explanation: 
Here in (i), when we update in Student table, Dept_id = Null, then it will not cause any problem to referenced table.
But in (ii) if we set in Department table, Dept_id = Null, then it will produce inconsistency because in Student table we will still have the tuples containing the Dept_id = 1.
There is 1 question to complete.