The correct answer is true.
Beowulf is a famous hero and he has fought many monsters and foes during his heroic career. On the other hand, Hrothgar is an old king, and he cannot fight anymore the way he used to when he was young. When Beowulf offers his help, Hrothgar gladly accepts it.
Grendel attacks Herot, Hrothgar's castle, and keeps on eating his men. This continues until Beowulf arrives with his own men, and manages to kill the monster and thus save Hrothgar and his people.