Trapped in a dungeon, you have found five keys, labeled A, B, C, D, and E. You have five locked doors, one in front of the other, numbered 1, 2, 3, 4, and 5. To escape, you must open all five doors. Each key opens exactly one door. The keyholes are coated with glue, so once a key is inserted, it can never be removed. Therefore, you must determine which key should be used for each door.
There are seven guards, all of whom are sympathetic and will help you leave. Still, they are nervous about being caught enabling your escape. Each one will answer just one yes-or-no question. All of the guards know which key goes with each door, and will answer either yes or no to the best of their knowledge.
The guards are impatient. After each answer you receive, you must ask the next question within about five seconds. Furthermore, the questions should be fairly simple, such as "Is B's door even?" The guards are not expert logicians or mathematicians, and will give up (and run away) if a question takes more than a minute for them to answer.
What questions should you ask?