Who was the Chairman of the Planning Commission?

Prime Minister of India

The correct answer is Option 2 - Prime Minister of India

Soon after India became independent, the Planning Commission came into being. The Prime Minister was its Chairperson. It became the most influential and central machinery for deciding what path and strategy India would adopt for its development.

The Government of India replaced the Planning Commission with a new institution named NITI Aayog. The Prime Minister was its Chairperson.
NITI Aayog stands for National Institution for Transforming India.
The NITI Aayog came into existence on 1 January 2015.