Normalisation closed

Question

Relation R is decomposed using a set of functional dependency F, and relation S is decomposed using another set of functional dependencies G. One decomposition is definitely BCNF, the other is definitely 3NF, but is not known to make a guaranteed identification. Which of the following tests should be used for the decomposition? (Assume that closure of F and G are available)  

A. Dependency preservation

B. BCNF definition

C. Both (A) and (B)

D. 3NF definition

I think D should be most appropriate answer but answer key has given it B.

Comments

This is gate question already asked . but by checking 3nf you cannot sure that next is BCNF or not B/c 3NF is subset of BCNF . since BCNF also satisfy 3nf property so how can we sure that relation is BCNF or 3nf.

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can you provide gate question link on GO ?

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Original question was which test will give guaranteed identification. That's why bcnf definition gives guaranteed identification as decomposed 3nf form fails it.