Which of the following statements about fourth normal form (4NF) is true?

1. A.

   A relation in 4NF must be in BCNF and should not have any non-trivial MVDs.

2. B.

   A relation in 4NF must be in 3NF and should have only trivial MVDs.

3. C.

   A relation in 4NF must be in 2NF and should not have any trivial MVDs.

4. D.

   A relation in 4NF must be in BCNF and can have non-trivial MVDs.

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