console 命令行工具 X clear
console
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>4</title>
</head>
<body>
    <select>
        <option value="请选择：" selected="selected">请选择：</option>
        <optgroup label="水果">
            <option value="pg">苹果</option>
            <option value="nht">猕猴桃</option>
            <option value="xz">杏子</option>
        </optgroup>
        <optgroup label="蔬菜">
            <option value="xhs">西红柿</option>
            <option value="bc">白菜</option>
            <option value="ymc">油麦菜</option>
        </optgroup>
    </select>
</body>
</html>
<br>
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