Which of the following/s is/are FALSE statement? A. An all key relation is…

Answer: D only (the statement that 3NF is stronger than BCNF is false).

• "An all key relation is always in BCNF since it has no FDs." — True. If a relation has no nontrivial functional dependencies (or if every nontrivial FD has a key or superkey as determinant), it meets the BCNF requirement that every nontrivial FD be determined by a superkey.

• "A relation that is not in 4NF due to nontrivial MVD must be decomposed to convert it into a set of relations in 4NF." — True. Decomposition is the standard method to eliminate nontrivial multivalued dependencies and achieve 4NF by splitting the relation into projections that remove the MVD-based redundancy.

• "The decomposition removes the redundancy by the MVD." — True. When you decompose a relation to resolve a nontrivial MVD, you remove the redundancy that arises from independent multi-valued attributes.

• "3NF is stronger than BCNF." — False. BCNF is stricter than 3NF: every BCNF relation is in 3NF, but there exist relations that are in 3NF and not in BCNF. Therefore the claim that 3NF is stronger than BCNF is incorrect.

Summary: Only the statement claiming that 3NF is stronger than BCNF is false, so the correct choice is the one that identifies that single false statement.