3.7序选择器/伪类选择器序选择器伪类选择器 nth-child(n/odd(奇数)/even(偶数)/表达式) */

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		/* 序选择器 伪类选择器 nth-child(n/odd(奇数)/even(偶数)/表达式)    */
		p:first-child{
			color: yellow;
		}
		p:last-child{
			color: pink;
		}
		p:nth-child(5){
			color: blue;
		}
		/* 选取奇数p标签 */
		p:nth-child(odd){
			background-color: red;
		}
		/* 选取偶数p标签 */
		p:nth-child(even){
			background-color: blue;
		}
		/* 1 4 7  3n+1 n是从0开始的 */
		p:nth-child(3n+1){
			font-size: 28px;
		}
		/* 2 5 8 3n+2 */
		p:nth-child(3n+2){
			width: 100px;
		}

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	<p>段落标签</p>
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