英语中，主动句和被动句都是表达句子中的动作或状态的方式之一。主动句指主语执行动作，而被动句则是主语承受动作。在不同的场合下，使用被动句可以使句子更加清晰明了，因此我们需要掌握如何将主动句转换为被动句。以下是一些例子：
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主动句：Tom writes letters every day. 被动句：Letters are written by Tom every day.
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主动句：The teacher explained the lesson to the students. 被动句：The lesson was explained to the students by the teacher.
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主动句：The company will launch a new product next month. 被动句：A new product will be launched by the company next month.
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主动句：The waiter served us dinner at the restaurant. 被动句：Dinner was served to us at the restaurant by the waiter.
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主动句：The company employs 500 workers. 被动句：500 workers are employed by the company.
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主动句：The government will build a new hospital in the city. 被动句：A new hospital will be built in the city by the government.
通过上面的例子，我们可以看到，将主动句改为被动句并不难，只需要将原句中的主语和谓语动词的位置对调，并在动词前加上be动词的适当形式即可。被动句的使用可以让我们的语言更加准确，也是书面语和学术论文中常用的表达方式。
