Question

Let R = (A, B, C, D, E) having following FDs. F = {A → BC, CD → E, B → D, E → A}

Which of the following is not a Candidate key?

1. A
2. B
3. E
4. BC

Answer 1

Correct Answer - Option 2 : B

A → BC

B → D

so A → D

so A → DC → E

Therefore A → ABCDE and hence A is a Candidate key

E → A

∴ E → ABCDE

Therefore E → ABCDE and hence E is a Candidate key

B → D

∴ B → BD

Therefore B → BD and hence BD is not a Candidate key

BC → CD

CD → E

∴ BC → ABCDE

Therefore BC is a candidate key