It foreshadows the outcome of the play. This is because it mentiones that they are dead. It allows you to guess what is going to happen next as both the lovers die and the families end their fued only after their children's death.
Basically the next time Grendel tried attacking Heorot Hall Beowulf was waiting for him and then attacked him then while wrestling with the demon Beowulf ripped his arm off. Grendel was severally injured so he fled into the woods and died. <span />
D is the answer. A hook needs to gain attention.