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Let $R=(A,B,C,D,E,F)$ be a relation scheme with the following dependencies:

$C\to F,E\to a,EC\to D, A\to B$.

Which of the following is a key for $R$?

1. $CD$
2. $EC$
3. $AE$
4. $AC$

(A)  $CD^{+}=CDF$

(B)  $CE^{+}=ABCDEF$  - correct answer

(C)  $AE^{+}=AEB$

(D)  $AC^{+}=ACB$
by
When We See a Production Rule Then We Realize That Only  C and E  Are Not genrated By Any Production  Then In the candidate Key It Has To be Presented Only When It Is Prime Attribute .

then Option B is Correct..

Or We Also Check Through By Doing Clouser Of Given Key..
Ans : b

(a)

CD+   =CDF

EC+ = ABCDE

AE+ = AEB

AC+= ABCF

SO OPTION B IS CORRECT.
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