You are conducting a cdp-based discovery using an edge switch for the seed.  there is a router between the switch and the wlse.  none of the access points are discovered， and the discovery log shows the switch is snmp unreachable. What is the problem？（）

• A、the snmp communities on the switch do not match the wlse.
• B、the snmp communities on the access points do not match the wlse.
• C、the snmp communities on the access points do not match the switch.
• D、the snmp communities on the router do not match the wlse.