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<html><head><script src="https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script><script>$(document).ready(function(){ $("p").on("mouseover mouseout", function(){ $(this).toggleClass("intro"); });});</script><style>.intro { font-size: 150%; color: red;}</style></head><body><p>Move the mouse pointer over this paragraph.</p></body></html>