<sup>用来标记作为上标的字符，表示幂的数学概念。<sub>用来标记为下标的字符，常用在脚注或化学式中。
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<div>化学方程式</div>
<p>2<sup>2</sup></p>
<p>2Mg+O<sub>2</sub>点燃2MgO</p>
<p>3Fe+2O<sub>2</sub>点燃Fe<sub>3</sub>O<sub>4</sub></p>
<p>4Al+3O<sub>2</sub>点燃2Al<sub>2</sub>O<sub>3</sub></p>
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来源：https://www.cnblogs.com/q2546/p/9327333.html