> none of the above was also a choice
Yes! The Seed of Doubt! If I ever have to create a multiple-choice test, this will always be one of the possible answers :-)
Just last month I had an exam where the examiner had already helped me correct a few basic errors by saying stuff like "well no you switched that around", then asked: "So what is the minimum distance here allowed by regulation?" Me: "Uuuuhh wait, it has to beeeee... 30!". Him: "So it's not 50 you sure?" Me: "wellllll Iii... (fuck you) no it's 30." Him: "Alright."
I had one physics teacher who taught us this lesson. he designed a test where some of the answer choices would be the same number but with a different number of significant figures (0 pts if you choose the wrong one). in a different section of the exam, he made answers that were deliberately off from the calculator result, and you had to know your sig figs to know if it was correct (none of the above was also a choice).
after that, we were all very happy to show our work on the remaining tests.