A、SNMPv3 enhanced SNMPv2 security features
B、SNMPv3 added the Inform protocol message to SNMP
C、SNMPv2 added the Inform protocol message to SNMP
D、SNMPv3 added the GetBulk protocol messages to SNMP
E、SNMPv2 added the GetBulk protocol message to SNMP
F、SNMPv2 added the GetNext protocol message to SNMP