需要使用<img>元素来向页面中添加图像。这是一个空元素（既没有结束标签）
<!DOCTYPE html>
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<html>
<head>
<title>TODO supply a title</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body>
<div>TODO write content</div>
<img src="images/quokka.jpg" alt="A family of quokka" title="the quokka is
an Australian marsupial that is similar in size to the domestic cat." />
</body>
</html>