I may be looking at your question too simplisticly. However, if you put two or more radio buttons on your form in design view, LC automatically groups the buttons so the default properties will be click one button and the other button will automatically uncheck.
View your form from the Preview PDF tab and test. Additionally, look in the heirarchy tab. You should see a Radio Button List with two or more untitled radio buttons under the List. As long as the actual buttons are in the list, you form should work properly.
