The correct answer should be B. living with others
Incongruity is when an event or action seems ridiculously out of place within a story. The correct answer is B, incongruity.
Is there anyway to emphasize that question you're asking?
Grendel attacks Heorot and devours the first warrior he encounters, when he tries to grab the second warrior, Grendel is shocked when the warrior grabs him back with great strenght (by the time the reader discovers this warrior was actually Beowulf).
Characters thoughts and actions
Characters appearances and ways of dressing
Characters responses to other characters