What Happens If You Don't Bother to Register a Copyright

What happens if you don't bother to register a copyright and someone pirates your work five years after it is published?

A) the copyright is lost by then.
B) it makes no difference whether you register-ever.
C) it makes no difference unless you also fail to include the copyright notice.
D) the copyright is still valid,but your remedies in an infringement lawsuit will be more limited.
E) the copyright will expire much sooner,but you can still sue the infringer.