Who is the chairperson of NITI Aayog?

The correct answer is Option (1) - Prime Minister

The Government of India replaced the Planning Commission with a new institution named NITI Aayog. NITI Aayog stands for National Institution for Transforming India. The NITI Aayog came into existence on 1 January 2015. The Prime Minister was its Chairperson.
Before the establishment of NITI Aayog, the Planning Commission operated for 65 years as it was formed in March 1950 and got replaced on 1 Jan 2015.
The Planning Commission was set up in March 1950 by a simple resolution of the Government of India.