In the sentence 'They live in the country', the plural form of the verb 'live' is in agreement with the plural subject 'they'.

在They live in the country一句中，动词复数形式live与复数主语they一致。

《牛津词典》

The singular form of the verb is always used with a compound or plural subject.

动词的单数形式总是和复合，复数的主语连用。

youdao

The evolution of the civil subject system, from unified subject to plural subject, is a complicated course.

民事主体制度的演进是一个从一元主体到多元主体的复杂历程。

youdao

The number of the subject (whether it's singular or plural) determines the number of the verb.

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