20. The assumption that a MAC number is registered by a manufacturer and cannot
ID: 3585773 • Letter: 2
Question
20. The assumption that a MAC number is registered by a manufacturer and cannot be used another manufacturer is represented by the functional dependency a. MAC- manufacturer. b. manufacturer-MAC. c. both d. neither. 21. Functional dependencies are constraints on a. a tuple in a relation b. a relation instance an attribute in a relation a component of a tuple c. d. 22. A relation decomposition must satisfy the lossless join property to prevent modification anomalies. a. insertion anomalies b. deletion anomalies c. d. spurious tuple generation 23. An attribute is prime if it is a member of a key not a member of any key c. a member of a superkey d. a member of all keys a. b. 24. A superkey is a set of attributes whose closure is the set itself the left hand side of some FD c. d. empty the set of all attributes a. b. 25. Suppose A->B is an FD and C is another attribute in the relation. Which FD must also be true? a. B->A b. AB->C C. AC->B d. BC->A 26. Given S, a set of FDs, in a relation. The FD A->B follows from S if a. A is a member of the closure of B b. A is not a member of the closure of B C. B is a member of the closure of A. d. B is not a member of the closure of A 27. R(A, B, C) is decomposed into R1(A, B) and R2(B, C). Which FD gives this decomposition the lossless join property? a. A->B b. A->C C. B->C d. C->BExplanation / Answer
20) b. manufacturer -> MAC.
Explanation:- Because given a MAC number we can determine the manufacture by the given assumption. Therefore manufacturer is functionally dependent on MAC.
21) c. an attribute in a relation.
22) d. spurious tuple generation
23) d. member of all keys
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