I-Clicker Monty Hall Problem

I was sitting in my ECON 102 lecture today when the professor posed a challenging I-Clicker question to the class. After a minute and a half he glanced at the computer monitor and announced that one of the most popular answers 'A' was incorrect. After the newly displaced answers found a new choice, he again declared that choice 'C' was incorrect, and announced that we now had a 50-50 chance of getting the right answer. I knew the professor's last remark was incorrect because I am a nerd (to be expounded upon in the appendix). I correctly identified the situation as a Monty Hall Problem, as it fit almost perfectly. The host is my professor, and the class as a whole is the contestant. I quickly crunched the numbers and found that after my professor revealed two answers were wrong, I would have a 75% chance of getting it correct if I switched to 'D'. According to the graph displayed after the question, 77% of the class answered D. I am aware that the close correlation in no way implies causation, but I found it interesting none the less.




Appendix: 
In the summer going into my junior year of high school, one of the books on the mandatory reading list was The Curious Incident of the Dog in the Night-time. The aforementioned novel tells the story about a severely autistic boy who has an extraordinary talent for math and his struggle to deal with his troubled home life. It is a good book; I recommend you all read it. In one of the chapters, the protagonist is explaining the powers of mathematics and he identifies a mathematician, Marilyn vos Savant, who was able to make a surprising conclusion from her solution to the Monty Hall Problem. The part about me being a nerd stems from the fact that the problem itself and its solution was included in an appendix to the novel which I, of course, read. Now, the only reason I remember the book is because of an inconsequential reference to an obscure math problem. As I previously stated, I am a nerd.