StdCtrls

Use TRadioButton to add a radio button to a form. Radio buttons present a set of mutually exclusive options to the user- that is, only one radio button in a set can be selected at a time. When the user selects a radio button, the previously selected radio button becomes unselected. Radio buttons are frequently grouped in a radio group box (TRadioGroup). Add the group box to the form first, then get the radio buttons from the Component palette and put them into the group box. 

By default, all radio buttons that are directly contained in the same windowed control container, such as a TRadioGroup or TPanel, are grouped. For example, two radio buttons on a form can be checked at the same time only if they are contained in separate containers, such as two different group boxes. 

TCheckBox 

TPanel 

TRadioGroup 

Buttons and Similar Controls 

Group Boxes and Radio Groups 

Radio Buttons