Which set of configurations resolves the issue?

Refer to Exhibit.

Traffic from the branch network should route through HQ R1 unless the path is unavailable. An engineer tests this functionality by shutting down interface on the BRANCH router toward HQ_R1 router but 192.168.20.0/24 is no longer reachable from the branch router .

Which set of configurations resolves the issue?
A . HQ_R1(config)# ip sla responder
HQ_R1(config)# ip sla responder icmp-echo 172.16.35.2
B . BRANCH(config)# ip sla 1
BRANCH(config-ip-sla)# icmp-echo 172.16.35.1
C . HQ_R2(config)# ip sla responder
HQ_R2(config)# ip sla responder icmp-echo 172.16.35.5
D . BRANCH(config)# ip sla 1
BRANCH(config-ip-sla)#icmp-echo 172.16.35.2

Answer: D

Explanation:

In the configuration above, the engineer has made a mistake as he was tracking 172.16.35.6 (the backup path) instead of tracking the main path (172.16.35.2). Therefore, when he shut down the main path, the track 1 was still up so traffic still went through the main path -> it failed.

To fix this issue, we just need to correct the tracking interface of the main path.