In optical channel transport unit overhead （OTU OH）， what are general communication channels 1 and 2（GCC1/GCC2） used for？（）

A.PPPoE can provide a host with access to a destination over Ethernet. You can have only one  PPPoE session per PVC
B.You must install PPPoE client software on all hosts that connect to the Ethernet segment. This means that the access provider must maintain a CPE
C.You cannot use PPPoE with Cisco Service Selection Gateway
D.PPPoE implementation is susceptible to broadcast storms and possible denial-of-service attacks
E.Per-session accounting is possible， which allows the service provider to charge the subscriber based on session time for various services offered. The service provider can also require a minimum access charge

A.prefix-list， route-map， filter-list， distribute list
B.route-map， filter-list， prefix-list， distribute-list
C.route-map， distribute-list， prefix-list， filter-list
D.filter-list， prefix list， route-map， distribute list
E.distribute list， prefix-list， route-map， fitter list

A.express mode
B.safe mode
C.loose mode
D.strict mode
E.tight mode