The more studying you did for the exam, the less sure you are as to which answer they want.
80% of the final exam will be based on the one lecture you missed and the one book you didn’t read.
Every instructor assumes that you have nothing else to do except study for that instructor’s course.
The night before the English History mid-term, your biology instructor will assign 200 pages on planaria.
If you are given an open-book exam, you will forget your book.
If you are given a take-home exam, you will forget where you live.