Hello!

Here is my solution. It holds its whole database in a tree of arrays. A
question node is a three-element array: [question, yes_tree, no_tree].
A leaf node is an array containing a single string.

It saves its data into ~/.animal-quiz using Array#inspect and reads it
using eval (to be simplistic).

It is located at <http://www.stber-koenig.de/ruby-quiz/>, along with
some other solutions for which I hadn't got time to submit.

Have a nice day!