Answer:
B
Step-by-step explanation:
As the definition of a tragedy is a literary work where the protagonist(s) is/are suffer(s) extreme sorrow, usually as a result of a tragic problem/defect, principle/moral weakness, or inability to deal with a circumstance(s). Answer B best matches this because the protagonists (the couple) are unable to stay together properly due to unfortunate circumstance, and because they are in love it is considered extremely sorrowful to them.
Hope this helps.