bcnf is not used meaning... relation can never be in bcnf if this criteria holds..
for A) B) C) we can make numerous examples that can be bcnf....and also numerous examples that can't be..
for D) relation(synonymous to table) has 2 mutually exclusive foreign keys meaning...
say R(abcdef) here a is key...d,f are referring to a ; so both of them are f.key. now as they are mutually exclusive we always have d-->f which is non-key ---> non-key
so this can't ever be a bcnf..