Interesting question and discussion.
I got it wrong (said 4) so I got my point. :w00t:
edit: But I'm still not sure whether the right answer is 1 or 2, even after reading all the discussion. I guess it depends on whether a B+tree indexing rows by column values is the same structure as a B+tree indexing some sort of pile of tokens attached to pointers (if that's what a full text index is - I don't really understand that either). :ermm: