a标签转为块级元素后为什么text-aling：center还起作用
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>Document</title>
<style>
ul {
margin: 0px;
list-style: none;
}
a {
display: block;
background: #ccc;
color: black;
text-decoration: none;
padding-bottom: 3px;
width: 120px;
line-height: 30px;
text-align: center;
}
a:hover {
background: darkorange;
color: white;
}
</style>
</head>
<body>
<ul>
<li>
<a href="#">首 页</a>
</li>
<li>
<a href="#">新闻快讯</a>
</li>
<li>
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