You have been asked to configure your router to send link-related SNMP trap notifications to the network managemetn system (NMS) located at address 172.16.17.1.Which two commands are required?（）

• A、set snmp trap-group my-trap-group targets 172.16.17.1
• B、set snmp targets 172.16.17.1
• C、set snmp trap-group my-trap-group link-status
• D、set snmp trap-group my-trap-group categories link