Why is wikipedia not considered a reliable source?

a)because there is not a printed version of it
b)because it can be easily changed by authors without expertise in the field
c)because too many people use it
d)because teachers say so

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