Radio buttons provide a way to present users with a number of mutually exclusive choices. Users can toggle the state of any radio button in a group between on and off. When the radio button is selected, its state is On and its value is registered. When the radio button is cleared, its state is Off and its value is not registered. Only one radio button object in a group can be in the On state.
Tip:
You can make a radio button look like a check box by setting its appearance characteristics in the Field tab of the Object palette. Before doing so, however, consider the expectations of users with respect to the behavior of check boxes. Do they expect check boxes to provide multiple choices? If so, you should maintain the standard and not apply radio button functionality to check box images.
After you add a radio button to the form design, you can edit the caption text and manipulate the object’s properties in the Field, Value, and Binding tabs of the Object palette. You can define these properties:
Radio buttons support scripting and calculations. If a user is to supply data, you can define whether the input is recommended or required, and you can set up messages to prompt users appropriately. User input may be validated through scripting.
An exclusion group is a group of radio buttons. Only one radio button in the exclusion group can be selected at a time.
You can work with an exclusion group as one object. Some options on the Object palette apply to all of the radio buttons in the same exclusion group. You can move radio buttons between exclusion groups and create new exclusion groups. If you have several radio buttons that are part of the same exclusion group, you can easily break some of the objects out into another exclusion group.
When you add a new radio button to the form, if the last object you added to the same subform was also a radio button, the new button will be part of the same exclusion group. If the last object you added was not a radio button, the radio button will create a new exclusion group.
Exclusion groups automatically resize to fit all of the radio buttons within the group. If you drag a radio button to an empty area of the page, the exclusion group will expand to contain the radio button. If you manually resize the exclusion group, all of the contained radio buttons will be resized accordingly.
See also 

Overview of radio buttons