Can I handle multiple choice options with conditions?

Is there a way I can add to a multiple choice question by adding an additional answer based on a conditional?

Unfortunately, it's not possible to handle check box options using conditions, you can only handle the entire field. 

You may however create multiple fields with the options you need to display and based on that show the check box or another field with the answers you need it to have. 

Please check this guide in order to get more details about how to show/hide fields based on user's answers: https://www.jotform.com/help/316-How-to-Show-or-Hide-Fields-Base-on-User-s-Answer 

I hope this helps.