If A+ and BC+ both produces all the attributes of the relation then candidate key would be A? or both A and BC?
You have to keep in mind that there can be more than one candidate key in a relation. It is the primary key that is one among those candidate keys.
So, as both A+ and BC+ both produces all the attributes of the relation then both of them are the candidate keys.
X->YZ , Y->XZ , ...