Step 1: Understanding the Concept:
NITI Aayog replaced the Planning Commission on January 1, 2015. It functions as the premier policy 'Think Tank' of the Government of India.
Step 2: Detailed Explanation:
The full form of NITI is "National Institution for Transforming India."
The word 'NITI' in Hindi also means 'policy' or 'ethics'.
The organization aims to foster cooperative federalism through structured support initiatives and mechanisms with the States on a continuous basis.
The options (B), (C), and (D) use similar-sounding words but are incorrect definitions of the acronym.
Step 3: Final Answer:
Option (A) provides the exact official full form of the institution.