What happened in the middle of the twentieth century that will not happen again for 4,000 years?

What occurrence provides the climax for the story “the occurence at owl creek bridge? a.)when peyton farquhar is standing on the bridge waiting to be hanged b.)when peyton farquhar reaches his home and sees his wife c.when peyton farquhar feels the pain in his back and finally dies d.)when peyton farquhar is running home and feels his tongue swelling