Given interface GigabitEthernet0/1 configured for VRRP group 115, which command set ensures this router becomes primary when it has the highest priority?

The vrrp 115 priority 100 command sets the VRRP priority for group 115 to 100. In VRRP, the router with the highest priority becomes the Master. If multiple routers have the same priority, the one with the highest IP address becomes Master. The default VRRP priority is 100. To ensure a specific router becomes primary, you would typically set its priority higher than other routers in the group. The options involving track are incorrect because tracking an object (like an interface or route) and decrementing priority is used for failover scenarios, not for initially setting a router as primary based on its inherent priority. While preempt allows a higher-priority router to take over, simply setting a higher priority is the fundamental way to designate a primary. The standby command is used for HSRP, not VRRP.