> Or maybe it's just that you need to pick something, so why not C?
Mostly this. That said, one definitely picks up when teachers bias the dice.
Some want an even distribution. If you confidently answered C's and D's early on and were later forced between A and C, A was the lucky bet. Other teachers avoided the first and last choices like the plague; this was common. With them, B and C (on a four-choice test) were the lucky bets.
Well with a sample size of one the 2022 test had 9/24 the answers as C which is above an expected (6/24) 25%.
Definitely some of the more annoying tests I've taken were when the answers were the same over and over. Its so weird to answer a T/F as T 10 times in a row and I've definitely lost points because I changed some of my Ts to Fs because I thought there was no way it was all Ts.
I've heard there's a tendency to put the "right" answer in the middle, especially if the answers to a question are numerical.
Or maybe it's just that you need to pick something, so why not C?