Let R = ( A, B, C, D, E, F ) be a relation scheme with the following dependencies:
C→F, E→A, EC→D, A→B. Which of the following is a key of R?
(A) CD
(B) EC
(C) AE
(D) AC
Answer: (B)
Explanation: To check find the closure for all
{CD} = {CDF}
{EC} = {ECDAFB} Only this is the key because it drives all attributes.
{AE} = {AEB}
{AC} = {ACBF}
Hence, Option (B) is Correct.
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