I really liked this one (the followup)
The question I referred you to fell squarely in that category. It was:
If you choose an answer to this question at random, what is the chance you will be correct?
They are missing the correct answer in the list! And adding the correct answer would change the answer - so that it might be incorrect as well. Meaning - there is more missing here than supplied. You don't stand a chance of answering the question at all.
I put forth that the answer is "e) none of the above" - making the right answer "20%".
Looking at the problem, if you assume the right answer is 25% - because you have a 1 in 4 chance of selecting any one of the items - the probability you will get the right answer randomly is 50%. So, it cannot be 25% - if it were - it would be 50% (confusing, yes).
Moreover, if you assume 50% is correct, then the right answer is 25% - because the chance of picking 50% is 1 in 4.
If you assume 60% is correct - well, I don't know what to say.
The question itself seems to somehow affect the answer - the act of answering the question changes the answer. Sort of like when you run a program in the debugger and it works perfectly - but when you run it standalone it crashes (that has never happened to me, nope, not a chance...).
So, my answer is "e) none of the above"