i think correct answer is option A as take for example,following :
Department Name
IT a
IT b
IT c
CSE d
CSE e
ME f
ECE g
now the result of above query will only show departments IT and cse as they are the only departments in which more than one student studies.
so,the output is non empty as we can also figure out that dept -> name does not hold because for two different value of names,we get same dept.
now,take another example:
Dept Name
CS a
IT b
ME c
--here ,output is empty,and we can also see that dept -> name holds as for two diff value of Name,we do not get same Dept.