Answer : 2. "Directive Principles of the State Policy "
Explanation :

The Unitary System of Government, where power is concentrated at the central level, ensures uniformity, efficiency, and quick decision-making in governance. This system allows for streamlined implementation of policies and laws without regional variations, leading to administrative simplicity. However, the Directive Principles of State Policy, while essential, are distinct principles in the Indian Constitution, guiding social and economic policies, irrespective of the system of government in place.