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<!DOCTYPE html> <html> <body> <select id="mySelect"> <option>苹果</option> <option>桔子</option> <option>凤梨</option> <option>香蕉</option> </select> <p>单击按钮可取消选择选项。</p> <button onclick="myFunction()">试一试</button> <script> function myFunction() { document.getElementById("mySelect").selectedIndex = "-1"; } </script> </body> </html>