How are the voice and web system parameter floater Ports used in Cisco Unified MeetingPlace Express?

A.
Can Allow the total system ports to be overbooked by this percentage that is 25 percent

B.
Are used for unexpected attendee needs and are taken out of the available scheduled ports pool

C.
Are used by Guest Attendees only

D.
Are only used by Cisco Unified MeetingPlace Express that are configured for all reservation less use (no scheduled meetings)