Which of the following statement(s) is/are true about the social system theory?

A. Barnard also laid a lot of emphasis on clear and formal as well as informal channels of communication as it was the life of a smooth functioning organisation

B. He defines an organisation as "a system of consciously coordinated activities or forces of two or more persons"

C. Barnard tries to understand human beings: one from within the organisation and two from outside the organisation

D. All of the above

Answer: Option D