a . Directive Principles of State Policy 

b . Fundamental Rights 

c . Preamble 

d . Seventh Schedule

Answer- a

Explanation:

The Indian Constitution explicitly declares that India will be organised as a social welfare state, ie, a state which renders social services to the people and promotes their general welfare.

This Concept of a welfare state is further strengthened by the Directive Principles of State Policy which set out the economic, social and political goals of the Indian Constitutional system

Hence, option a is correct.

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