Where Did the Phrase "Mad as a Hatter" Come From

Where did the phrase "mad as a hatter" come from?

A) People wore hats in the 1800s to signify mental illness.
B) Hat makers were notorious in old England for their angry and violent tempers.
C) Hat makers were poisoned by mercury in hat factories and madness was a symptom.
D) Lewis Carroll coined the term in his Alice in Wonderland, and it has been used ever since.
E) A well-known insane asylum in England was called Hatfield, and the residents were called "hatters."