I believe the answer is: B. To show that Grendel cannot rely on nature for protection
In the story, Grendel perceive that he is blessed by protection from the nature which would always help him in all of his troubles. But when he somehow got his foot stucked in a tree in front of a bull and when he cried and scream for help from the nature, he did not receive any answer.
A gerund is basically a verb that ends in ‘ing’
For example : James loves singing.
