Which concept does Talcott Parsons use to indicate the increasing complexity of social organization?

Differentiation

Explanation:

Differentiation is the process by which different subsystems of a society replicate in order to increase the complexity of society. Each subsystem can work independently and can interact with other subsystems which over time increases complexity.

As a result of differentiation factors of the environment can be better managed.

Hence, the question is referring to differentiation.