Statement A is incorrect: It talks about the State’s inability to enforce its will, which is not the focus of the passage.

Statement B is incorrect: This refers mainly to self-development of members, not the role of buffering against State power.

Statement C is incorrect: It talks about participation and common endeavour, but does not explain how associations act as a buffer between individual and State.

Statement D is correct: A network of voluntary associations allows individuals to divide their loyalties among multiple groups, preventing the State from becoming overly powerful and thus acting as a buffer.