You wait until you have to sit your ATPL Exams - where you have to answer the question wrong in order to get it marked right... or have a question which has no right answers..
Or like me - get the exact same question TWICE in an exam, with different answers available, on one question you had to round your figures up to get it right and on the other question (SAME question different answers, including the answer from the first question) had to not do any rounding up/down at all to get the mark!! Obviously in the exam under pressure I had already worked it out once so was not going to work it out again - and thus dropped my only mark of the exam!
Or the other exams in the Bristol Question Bank that state something like "if you see this question in an exam appeal it as its factually wrong!"