spoken是动词speak的过去分词形式，在句中作定语，修饰主语language, spoken 与 language有被动关系。该句可以理解为

What’s the language (which is) spoken in German?

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汉语的受事主语句是话题的形式特征+ T触发动词的域内论元移位的结果。

Chinese Patient-subject Sentences result from the movement of the verbal internal argument triggered by the formal feature + t of the topic.

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数的形式如果这种主语指的是一类人动词用复数如果指的是单个人或抽象概念，动词用单数。的是单个人或抽象概念动词用单数。

With such a subject, the choice between a plural or a singular verb depends on whether the adjective refers to a group of people or to a particular person or an abstract quality.

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