Final answer:
The irony in 'joy that kills' suggests that what seems like a positive emotion, happiness, unexpectedly causes a tragic outcome, which is Louise's death upon her husband's return. This highlights the contradictory nature of emotions and how they can lead to unforeseen consequences in literature.
Step-by-step explanation:
The irony in the phrase 'joy that kills', which ultimately leads to the death of Louise in Kate Chopin's short story, stems from the fact that joy is typically associated with positive outcomes, not tragic ones. However, in this context, it is the overwhelming feeling of joy and freedom that Louise experiences upon believing that her husband has died that leads to her heart failing when he surprisingly returns alive. This turn of events embodies the irony of the situation, as the happiness Louise felt due to her newfound independence is abruptly taken away, literally leading to her demise.
Answer choice (b) It suggests that happiness can lead to tragedy is the correct interpretation of the irony in this phrase. The unexpectedness of a positive emotion resulting in a negative outcome—Louise's death—underlines the complex nature of human emotions and fate. Moreover, it highlights the contradictions and complexities of human existence, challenging the notion of simple and direct messages in literature.