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<html><script src= "https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script><script>$(document).ready(function(){ $("button").click(function(){ $("h1, h2, p").toggleClass("blue"); });});</script><style>.blue {color: blue;}</style><body><h1>Heading 1</h1><p>This is a paragraph.</p><button>Toggle class</button></body></html>