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    Question

    Given a relation R(A, B, C, D, E) and functional

    dependencies {A -> B, BC -> D, D -> E}. Which of the following is a candidate key for R?
    A A Correct Answer Incorrect Answer
    B AC Correct Answer Incorrect Answer
    C BC Correct Answer Incorrect Answer
    D AD Correct Answer Incorrect Answer
    E BD Correct Answer Incorrect Answer

    Solution

    (AC)+ = A, C, B (from A->B), D (from BC->D), E (from D->E). So (AC)+ = {A, B, C, D, E}. No proper subset of AC can determine all attributes.

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