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<html><body><form action="/action_page.php"> Radio Button: <input type="radio" id="myRadio" name="test"> <input type="submit"></form><p>Click the "Try it" button to set the required property for the radio button.</p><p><strong>Tip:</strong> Click the "Submit" button before and after you have clicked the "Try it" button, to see the effect.</p><button onclick="myFunction()">Try it</button><p id="demo"></p><script>function myFunction() { document.getElementById("myRadio").required = true; document.getElementById("demo").innerHTML = "The required property was set. The radio button must now be checked before submitting the form.";}</script></body></html>