Consider the following query :
SELECT E.eno, COUNT(*)
FROM Employees E
GROUP BY E.eno
If an index on eno is available, the query can be answered by scanning only the index if

A

the index is only hash and clustered

B

the index is only B+ tree and clustered

C

index can be hash or B+ tree and clustered or non-clustered

D

index can be hash or B+ tree and clustered