The first option is most salient, by virtue of being first.
Level 0 players will tend to choose option 1. Level 1 players will realize that this is what level 0 players will do, so they will tend to choose option 2 ("the first one"). Level 2 players will realize that this is what level 1 players will do, so they will tend to choose option 4 ("the second one"). Level 3 players will realize that this is what level 2 players will do, so they will tend to choose option 5 ("the fourth one"). Apparently there are lots of level 1 & 2 players, but very few level 3 players.
But this analysis does not explain why so many people chose option 3 ("the last one") - I doubt that they are level 4 players. Perhaps it's that the last answer is the second-most-salient, by virtue of being last, making them level 1 players with a twist.
When trying to choose randomly, people tend to avoid options with salient features. It is not so easy to sort players into levels accurately.
Today's Poll of the Day at gamefaqs.com poses an "interesting" question...
Which poll answer do you think will be the most popular today?
I guess it's sort of like the minority game? Anyone want to try to analyze this?