Step 1: Understanding the Concept:
The question asks for the primary justification for providing reservations (affirmative action) to the Scheduled Castes (SCs) in India.
Step 2: Detailed Explanation:
The policy of reservation for Scheduled Castes is rooted in the historical context of the Indian caste system.
- The core reason is to provide social justice and remedy the centuries of discrimination, oppression, and exclusion faced by communities who were considered "untouchable". This status of "untouchability" is a direct consequence of their low ritual position in the caste hierarchy.
- While this discrimination led to extreme poverty (A) and economic deprivation (B), these are consequences of the primary social problem. The reservation policy aims to correct the root cause, which is the social backwardness and stigma attached to their ritual status.
- Population (C) is a factor used to determine the \textit{quantum} or percentage of reservation, not the \textit{reason} for providing it.
Step 3: Final Answer:
The fundamental reason for providing reservation to Scheduled Castes is to compensate for the historical injustice and social disabilities arising from their low ritual position and the practice of untouchability.