Implementing Cisco IP Switched Networks (SWITCH v2-0) (#78)

Which statement about the use of PagP link aggregation on a Cisco switch that is running Cisco IOS Software is true?

PagP modes are off, auto, desirable, and on. Only the combinations auto-desirable, desirable-desirable, and on-on allow the formation of a channel.
PagP modes are active, desirable, and on. Only the combinations active-desirable, desirable-desirable, and on-on allow the formation of a channel.
PagP modes are active, desirable, and on. Only the combinations active-active, desirable-desirable, and on-on allow the formation of a channel.
PagP modes are off, active, desirable, and on. Only the combinations auto-auto, desirable-desirable, and on-on allow the formation of a channel.