Optional Comments Underneath a Survey Question

What are the steps/processes in order to be able to edit a survey page to allow optional comments underneath each question?

I would like the user to select a radio button titled "Comment?" and from there on pops up a textbox to be able to comment on the question asked. It doesn't even HAVE to be a radio button.

Also, how do I get it to push the data over to responses. It should then show up in the response view. Someone please help.

Thanks!