Answer:
C. Go into those unknown lands and find Grendel's mother, if you are brave enough.
Step-by-step explanation:
This is the best way to convey the literal meaning of this quote. In this quote, we learn that the hero is to go to "the land thou knowst not." This refers to the land that the hero has not yet explored. Moreover, afterwards, he is to find the "sin-flecked being." This would be a being that is sinful, and the description most likely refers to Grendel's mother. "Seek if thou dare" is an invitation for the hero to question whether he is actually prepared and brave enough to face such danger.