【单选题】

The Simple Network Management Protocol (SNMP)is an (66) protocol that facilitates the exchange of management information between (67) . It is part of the TransmissionControl Protocol/Internet Protocol(TCP/IP) protocol suite. SNMP enables network (68) to manage network performance, find and sole network problems, and plan for (69) An SNMP -managed network consists of three key components: managed devices , (70) ,and network -management systems .

A．Physical Layer
B．Link Layer
C．Network Layer
D．Transport Layer