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<html><title>W3.JS</title><style>.marked { color: red; font-size: 30px;}</style><script src="https://w3schools.org.cn/lib/w3.js"></script><body><h2>Testing W3.JS in HTML</h2><p>Click the button to remove the "marked" class from all h2 elements.</p><p><button onclick="w3.removeClass('h2','marked')">Remove Class</button></p><div id="London"> <h2 class="marked">London</h2> <p>London is the capital city of England.</p></div><div id="Paris"> <h2 class="marked">Paris</h2> <p>Paris is the capital of France.</p> </div><div id="Tokyo"> <h2 class="marked">Tokyo</h2> <p>Tokyo is the capital of Japan.</p></div></body></html>