When a generalization is made, is it always possible to have a complete enumeration?

Yes, because if there is not a complete enumeration, then you can't make a generalization at all.

No$,$ because there can only be a complete enumeration when there are fewer than $50$ instances.

No$,$ because it is never possible to have a complete enumeration.

No$,$ because sometimes there are too many instances to examine them all.

Yes, because even an infinite number of instances could be thoroughly examined in a finite number of clusters.