Refer to the exhibit.
R1 is configured with IP SLA to check the availability of the server behind R6 but it kept failing. Which configuration resolves the issue?
A. R6(config)# ip sla responder
B. R6(config)# ip sla responder udp-echo ip address 10.10.10.1 port 5000
C. R6(config)# ip access-list extended DDOS
R6(config ext-nac)# 5 permit icmp host 10.66 66.66 host 10.10.10.1
D. R6(config)# ip access-list extended DDOS
R6(confg ext-nac)# 5 permit icmp host 10.10.10.1 host 10.66.66.66
