正解:B
In the context of HSRP, the standby 2 preempt command enables a router to become the active router when it has a higher priority than the current active router. If Router 1 is set with a priority of 110 and it fails, causing Router 2 to take over as the active router, then when Router 1 comes back online, it will not automatically take back the role of active router unless it is configured with the preempt command. The preempt command allows Router 1 to reclaim its role as the primary HSRP router due to its higher priority. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) training materials or official certification guide.