I think Grendel get stuck in a tree because of his careless curiosity of the world above him, that of the humans. He know nothing about that world because he was used to his own world in the underground however he still get tempted to explore. He was also attacked by a bull there because he looks different from the rest of the creatures above.
It’s the one that has (page20) at the end
Number one is c
number two is d
number three is c
number four is a
hope that helps you
