Metaphor is elucidated as the literary device that includes a comparison of two distinct and literally inapplicable ideas to invoke an implied similarity between them that assists in explaining or clarifying the idea.
In the given example, the use of 'cup' to describe 'endurance', 'abyss' to 'injustice', 'bleakness and corroding' to depict the 'despair' exemplify the unrelated, literally inapplicable, and implied comparison to reveal the similarities between them that helps the author to clarify the idea more effectively. Thus, <u>'metaphor'</u> is the correct answer.
