A.3
B.4
C.5
D.2
E.6

A.SNMP version 2 uses a proxy agent to forward GetNext message to SNMP version 3.
B.SNMP version 2 supports message integrity to ensure that a packet has not been tampered with
C.Proxy agents were used only in SNMP version 1.
D.SNMP version 3 supports encryption and SNMP version 2 support authentication.
E.GetBulk messages are converted to GetNext messages by the proxy agent and are then forwarded to the SNMP version 1 agent.