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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(){ $("button").click(function(){ var btn = $(this).text(); $("p").css("background-color", "white"); $("p" + btn).css("background-color", "yellow"); });});</script></head><body><p>The first paragraph in body, and the first child in div.</p><div style="border:1px solid;"> <p>The first paragraph in div, and the first child in div.</p> <p>The last paragraph in div, and the last child in div.</p></div><br><div style="border:1px solid;"> <span>This is a span element, and the first child in this div.</span> <p>The first paragraph in another div, and the second child in this div.</p> <p>The last paragraph in another div, and the third child in this div.</p> <span>This is a span element, and the last child in this div.</span></div><br><div style="border:1px solid"> <p>The first paragraph in another div, and the first child in this div.</p> <p>The last paragraph in the another div, and the last child in this div.</p></div><p>The last paragraph in body, and the last child in div.</p><button>:first</button><button>:first-child</button><button>:first-of-type</button><br><br></body>