Final answer:
At level 11, barbarians gain the abilities Relentless Rage and Persistent Rage.
Step-by-step explanation:
At level 11, barbarians gain the abilities Relentless Rage and Persistent Rage. Relentless Rage allows barbarians to keep raging even if they drop to 0 hit points, as long as they succeed on a DC 10 Constitution saving throw. Persistent Rage allows barbarians to keep raging beyond the normal 1 minute duration without needing to take damage or make an attack. This ability allows barbarians to maintain their rage for extended periods of time, providing them with increased damage resistance and other benefits.