Custom answer in radio or drop down menu fields?

I would like for there to be a way for my customers to type in a custom reponse in a radio button or drop down menu if the ones I already have don't fit. For example, if I ask customers how they discovered my site and I have radio buttons like: radio, newspaper, magazine, google. etc. I also want there to be a way for them to type in their own custom answer if they found me from a specific link or other media. I also have a drop down menu with 2 different sentences they can choose, but I'd like to be able to let them type out their own custom sentence if they prefer. Is there a way to do this? Thanks for your help! Basically, I'm asking can users type things into any areas that aren't text fields/boxes to begin with?

If you use a check-box you can enable the "other" option that allows users to type a different option:

If you wish users to choose only one option you can go to properties and edit the maximum selections allowed:

In alternative if using a radio-button or dropdown, you can use conditional logics so that if user selects on option, a specific field will show:

Please test and clone this form if you wish:

http://form.jotformeu.com/form/41185487473362

Let us know if we can be of assistance.