Refer to the exhibit. The failover time of ISP-2 is significantly shorter than ISP-1 when an interface on the ISP router toward the campus network fails. Which ...

Refer to the exhibit. The failover time of ISP-2 is significantly shorter than ISP-1 when an interface on the ISP router toward the campus network fails. Which solution minimizes the downtime to the sub-second?

A. Aggressive timers B. Next-hop address tracking C. Graceful-restart D. BFD