Suppose we are told that a relation S$($A$,$ B$,$ C$,$ D$)$ is in BCNF$,$ and that exactly $3$ out

of the $4$ FDs listed below hold for S$.$ Choose the FD from the list below that does not

hold on S because it violates BCNF$.$ Hint: consider the possible scenarios when you

have $3$ out of $4$ FDs that hold. For each scenario, determine if the fact that S is in BCNF

is true in that scenario.

$1$: A$->$BCD

$2$: BC $->$ A

$3$: CD$->$B

$4$: D$->$C