Databases: Candidate Keys Question

Please Explain How To Find Parts A and B for these questions?

NOTE: The answers have been provided... Just explain how to find parts A and B for each

Exercise 19.7 Suppose you are given a relation R with four attributes ABCD. For each of the following sets of FDs, assuming those are the only dependencies that hold for R, do the following: (a) Identify the candidate key(s) for R. (b) Identify the best normal form that R satisfies (1NF, 2NF, 3NF, or BCNF). (c) If R is not in BCNF, decompose it into a set of BCNF relations that preserve the dependencies. 2. B C, D A 3. ABC D, D- A 4, A ? B, BC ? D, A ? C 5, AB ? C, AB ? D, C ? A, D ? B