Generally Normalization is done on the schema itself.
From the relational instance given,we may strike out FD s that do not hold.
e.g.B does not functionally determine C(This is true).
But we cannot say that A functionally determines B for the entire relation itself.This is because that ,A->B holds for this instance,but in future there might be some tuples added to the instance that may violate A->B.
So overall on the relation we cannot conclude that A->B,from the relational instance which is just a subset of an entire relation.