Router A (priority 110) and Router B (priority 100) run HSRP with preempt enabled on both. Router A has 'standby 1 track GigabitEthernet0/1 decrement 20'. GigabitEthernet0/1 on Router A fails. Which router becomes active for the HSRP group?

When GigabitEthernet0/1 on Router A fails, the track command causes Router A's HSRP priority to decrement by 20. Its new priority becomes 110 - 20 = 90. Router B's priority remains 100. Since Router B now has a higher priority (100 vs. 90) and preemption is enabled on both routers, Router B will preempt Router A and become the active router for the HSRP group. Router A remaining active is incorrect because its priority drops below Router B's. Both routers entering standby is incorrect as HSRP always elects an active router if available. The router with a lower IP address is only considered in a tie-breaker scenario, which is not the case here.