Is there a hack or rewrite for the registration page

say the user has an extra line where they need to answer a question correctly

I know one can be added as ENTER THE LETTERS IN THE IMAGE YOU SEE HERE
but sometimes the text is just too crazy and people get lazy.

Lets aay i wanted to add a registration line saying

In what country is PARIS located?
They would have to type FRANCE

anything else or left blank would result in an incomplete registration