The correct answer is option 3 - Prime Minister. The Planning Commission is a government body in India responsible for formulating and implementing economic and social development policies. It was established in the year 1950 and operates under the authority of the Prime Minister. The Chairman of the Planning Commission is appointed by the Prime Minister, who holds the highest authority in the commission. The Chairman plays a crucial role in guiding and steering the planning and development agenda of the country. The President of India, option 1, does not have a direct role in the functioning of the Planning Commission. The Finance Minister, option 2, may provide inputs and support, but is not the Chairman. Option 4, Minister for Planning, does not exist, and is incorrect. Therefore, the correct answer is option 3 - Prime Minister.