normalization

Question

Answer 1

Option D is right.

Comments

and dependency also preserved since AB->CD and C->A  can give BC->CD  which is present in CBD  and from BC->CD and C->A we can get AB->CD

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Sorry wrote mistake.

Option d is right.we can not derive functionl dependency AB-->CD.

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why dependency is not preserved can't we do like this

AB->CD and C->A  can give BC->CD  which is present in CBD  and from BC->CD and C->A we can get AB->CD