A Scholar will appear in one of your capital cities after every couple of successful missions and he will have 5 questions for you. This is probably one of the most tedious achievements in the game, however there are solutions for this. After you have unlocked all of the capital cities the Scholar will just stay in the cities forever and you can continually speak with him to take the quiz. The odds of getting asked a question you already got correct are very slim so once you've answered a question right you probably won't see it again until you have unlocked this achievement.
Now for those of you fortunate enough to have a controller with turbo on it you can actually do this in your sleep, after you have unlocked all the capital cities speak with the Scholar and then set your turbo setting to on for the button and the game will answer the Scholar's questions at lightning speed which is much quicker than looking up the answers manually. Leave it on overnight and wake up with your achievement.
GameFAQs Dynasty Warriors 7: Scholar Quiz Guide
[Special Thanks to CEmAN4 of GameFAQs for this guide]