Correct Answer: C
To configure and verify router R3 to measure the response time to the file server, the correct command set involves enabling IP SLA responder and configuring an IP SLA probe. The IP SLA responder is configured on the target device, in this case, the file server, to respond to the IP SLA probe sent by R3. The probe is configured on R3 to send a specific type of test traffic to the responder, and the response time is measured based on the round-trip time of the packets.
Option C is the correct choice because it includes the commands to set up an IP SLA ICMP-echo operation, which sends ICMP echo requests from R3 to the file server's IP address. The ip sla schedule command is used to specify the operation number, start time, life of the operation, and frequency of the test.
https://www.cisco.com/c/en/us/support/docs/smb/switches/cisco-550x-series-stackable-managed-switches/smb57