ibps-so 2016 · Question 179 of 394

The redesigned relation AGENT, an instance of which is shown below, carries for every business correspondent an agent_id allotted by the bank, the PAN of the agent, the mobile number registered with the bank, and the code of the branch that services him. No two agents share an agent_id; no two share a PAN; two agents may and do share a mobile number, and many share a branch. agent_id pan mobile branch_code AG-104 AKPPM4471C 9820011223 BR-018 AG-217 BQTPS9038L 9370044556 BR-018 AG-350 CDMPR2214J 7719088990 BR-042 AG-486 DNRPK6672F 9370044556 BR-042 agent_id has been declared the primary key. On these facts the correct statement is that:

1. Apan is not a key at all, since a key must be allotted by the organisation that owns the relation
2. Bmobile is a candidate key, since it is a contact number and each agent has one
3. Cthe pair (agent_id, mobile) is a candidate key, since together the two values certainly identify a row
4. Dpan is a candidate key which, not having been chosen as the primary key, is an alternate key; the pair (agent_id, mobile) is a superkey but not a candidate key; and branch_code is neitherCorrect
5. Ebranch_code is an alternate key, since it may be used to reach a group of rows when agent_id is not known