Step 1: Understanding the Concept:
The question is about a significant reform in India's governance structure, specifically the body that succeeded the Planning Commission.
Step 2: Detailed Explanation:
The Planning Commission was an institution in the Government of India that formulated India's Five-Year Plans. It was established in 1950.
In 2014, the Government of India announced its decision to dissolve the Planning Commission.
It was replaced by a new institution called NITI Aayog (National Institution for Transforming India) on January 1, 2015.
NITI Aayog acts as the premier policy 'Think Tank' of the Government of India, providing both directional and policy inputs. Unlike the Planning Commission, it does not have the power to allocate funds.
The Finance Commission and Inter-State Council are different constitutional bodies with distinct functions.
Step 3: Final Answer:
The institution that replaced the Planning Commission is NITI Aayog. Option (C) is the correct answer.