The correct answer is: Manik Sarkar.
Manik Sarkar was the Chief Minister of Tripura from 1993 to 2018. He was the longest-serving Chief Minister of any state in India. He was a member of the Communist Party of India (Marxist) (CPI(M)).
Agatha Sangma is a member of the Indian National Congress (INC). She was the Chief Minister of Meghalaya from 2010 to 2018.
Prakash Karat is a member of the CPI(M). He was the General Secretary of the CPI(M) from 2005 to 2015.
Ikram Obibi Singh is a member of the Indian National Congress (INC). He was the Chief Minister of Manipur from 2002 to 2007.