I went with "other". I generally follow option 2, but have sort of a "keep the game moving" house rule. To wit: If you can't find the answer to question quickly, make something up and move on with the game. After the game, learn the real rule (or make a house rule) so this situation doesn't slow us down next time.
I rarely if ever feel it necessary to "ignore the rules to make the plot of the game go the way I want it to." First, that sounds a bit like railroading. Second, I feel I owe the players a sense of consistency and the rules + my house rules are a stable body of world physics that they can rely upon. Third, as DM, I wield enough power as it is to manipulate the game; I don't need to rob the campaign of consistency in order to facilitate the fun of the game.
Finally, you can do a lot with the "DM's best friend."