Explanation:

- Option 1: Class struggle

- This concept originates from Marxist theory and refers to the conflict between different classes in society, typically between the bourgeoisie and the proletariat. It’s not related to indirect cooperation.

- Option 2: Division of Labour

- Division of labour refers to the specialization of tasks in a work environment where individuals perform specific roles or jobs. This principle enhances efficiency and is fundamental to indirect cooperation, where different specialized roles collectively achieve a common goal.

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- Option 3: Positivism

- Positivism is a philosophical theory that asserts knowledge is derived from empirical evidence and observable phenomena. It is unrelated to indirect cooperation mechanisms.

- Option 4: None of the above

- This option implies that indirect cooperation does not rely on any listed principles, which is incorrect as Division of Labour is relevant here.

Your understanding of the principle governing indirect cooperation is correct.