The correct option is A Bhimrao Ramji Ambedkhar
On 30 September 1956, B. R. Ambedkar had announced the establishment of the "Republican Party of India" by dismissing the "Scheduled Castes Federation", but before the formation of the party, he died on 6 December 1956. After that, his followers and activists planned to form this party. Hence, Option A is correct. Among the rest of the options, Somnath Lahiri and Jawaharlal Nehru did not found any party, while Shyama Prasad Mukherjee founded the Bharatiya Jan Sangh. Hence, these are incorrect.