ANSWER: When the Confederate soldiers come through town, they remove all of the Union flags. Barbara Frietchie is upset that her flag was removed. She puts her flag back up in the attic window, risking her life to stand up for what she believes.
Hey there! :D
Coincidence is the chance that two ironic things would happen at once. It's like a random thing that you wouldn't suspect to happen.
So, the best answer is "A" chance.
I hope this helps!
~kaikers