Consider R(A, B, C, D, E) be relation with following dependencies: C->F, E->A, EC->D, A->B. Which of the following is a key for R ?

1. ACD
2. BEC
3. CAE
4. DAC

Pick an option to check yourself, or open the answer below.

Show answer & explanation

Correct answer: B. EC

Explanation

E and C never appear on a right side, so every key must contain both. (EC)+ = E, C, A (E→A), D (EC→D), B (A→B): all attributes. So EC is the key.