Answer:
I think B.
Brett grabs Tor's arm and give him a warning
The passage lists a few things which would lend towards the idea of him being a monster. First, it says "god's anger bare he." referring, presumably, to the abrahamic god famous for his wrath, showing that Grendel was exhibiting intense rage. Second, it uses the sentence "The monster intended some one of earthmen in the hall-building grand to entrap and make way with" which, while a written a little backwards by today's grammar rules, says that he is planning to take hold of and kidnap some of the men in the hall, something only a monster could do.<span />
Avoid it, not go near, stay away.
