Answer:
D. Betrayal.
Step-by-step explanation:
Betrayal is an act of deliberate disloyalty to someone. In the given summary of a specific part of the plot of "The Metamorphosis" by Franz Kafka, we can see an example of betrayal, because at the end of the story Grete, who initially protects her brother and makes sure that no one hurts him, starts to be against him and even want her parents to get rid of him, being disloyal on purpose.