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<html><body><form> What color do you prefer?<br> <input type="radio" name="colors" id="red">Red<br> <input type="radio" name="colors" id="blue">Blue</form><button onclick="check()">Check "Red"</button><button onclick="uncheck()">Uncheck "Red"</button><script>function check() { document.getElementById("red").checked = true;}function uncheck() { document.getElementById("red").checked = false;}</script></body></html>