RadioButton 
The RadioButton UI element is a button with two states (on/off) that enables users to select options. The RadioButton allows you to spread the displayed radio buttons individually on the screen instead of grouping them in a table. You can toggle the radio button when you bind the UI elements to the same context attribute. The radio button is selected if the context attribute to which the selectedKey property is bound contains the value of the key that belongs to this radio button. The key is specified by property keyToSelect.
activateAccessKey
Indicates whether access key for this control is activated. More information: Enabling Access Keys
explanation
Determines the explanation text. More information: Explanation
keyToSelect
This property specifies the value of the key used to select this radio button.
selectedKey
Specifies the path of the context attribute that stores the selected key.
readOnly
Specifies whether or not the user can make selections in the checkbox.
state
Describes the error status of the UI element. The data type of this property corresponds to enumeration type WDState. You can use the values normal and required.
text
This property describes the text next to the radio button.
textDirection
Specifies the text direction and allows you to use a radio button for texts in languages which require a specific text direction.
onSelect (String key)
This event is triggered when the user selects the radio button.