Choose the most appropriate answer: which institution is the official think tank of the Government of India that replaced the Planning Commission on 1 January 2015?

Introduction / Context:
The question checks awareness of contemporary institutional changes in Indian economic governance. Until 2014, the Planning Commission framed five year plans and played a central role in resource allocation. From 1 January 2015, the Government of India formally replaced it with a new body that serves as a policy think tank and advisory institution rather than a centralised planning authority. Knowing this change is important for general studies and current affairs based examinations.

Given Data / Assumptions:

• The Planning Commission has been abolished.
• A new institution started functioning from 1 January 2015.
• This new body is described as the think tank of the Government of India.
• Four possible names using the acronym NITI are given in the options.

Concept / Approach:
The official replacement for the Planning Commission is the National Institution for Transforming India Aayog, popularly known as NITI Aayog. It provides directional and policy inputs to the Union and State Governments, focusing on cooperative federalism, long term strategies and evidence based policy making. The correct option must match the official name used in government notifications, budgets and policy documents, not a made up phrase that only resembles this name.

Step-by-Step Solution:
Step 1: Recall that the Planning Commission was replaced from 1 January 2015. Step 2: Remember that the new body is called the National Institution for Transforming India Aayog. Step 3: Observe that this full name is commonly shortened to NITI Aayog in all official and media references. Step 4: Compare each option and select the one that exactly matches this short official name. Step 5: Conclude that NITI Aayog is the correct answer and the other NITI names are distractors only.

Verification / Alternative check:
A simple way to verify is to recall that NITI expands to National Institution for Transforming India. None of the distractor options has any basis in government usage, while the term NITI Aayog appears frequently in Union Budget speeches, NITI discussion papers and official websites. Coaching material and standard polity books also clearly state that NITI Aayog replaced the Planning Commission from 2015, confirming this choice.

Why Other Options Are Wrong:
NITI Dharma has no existence as an institution of the Union Government and is created only as a confusing phrase. NITI Vakya is also a made up name that may sound Sanskrit but is not used officially. NITI Vajpayee appears to link the acronym to the name of a former Prime Minister but there is no such body. None of these three options is mentioned in any constitutional or statutory context.

Common Pitfalls:
A common mistake is to overthink the meaning of the acronym and choose an option that appears morally or culturally appealing, instead of recalling the official name. Another error is to confuse NITI Aayog with older bodies like the National Development Council or the Planning Commission itself. Students should also avoid spelling based errors where they misread Aayog as Ayog or some other form, even though that would still refer to the same institution in English usage.

Final Answer:
The think tank that replaced the Planning Commission on 1 January 2015 is NITI Aayog, which stands for the National Institution for Transforming India Aayog.