Explanation:

Shripad Amrit Dange (10 October 1899 – 22 May 1991) was a founding member of the Communist Party of India (CPI) and a stalwart of Indian trade union movement. During the British Raj, Dange was arrested by the British authorities for communist and trade union activities and was jailed for an overall period of 13 years. After India's Independence, a series of events like Sino-Soviet split, Sino-Indian war, and the revelation that while in jail, Dange had written letters to the British Government, offering them cooperation, led to a split in the Communist Party of India, in 1964. The breakaway Communist Party of India (Marxist) (CPI(M)) emerged stronger both in terms of membership and their performance in the Indian Elections. Dange, who remained the Chairman of the CPI till 1978, was removed in that year because the majority of party workers were against Dange's political line of supporting Indian National Congress, and Indira Gandhi, the then Congress Prime Minister. He was expelled from the CPI in 1981. He joined the All India Communist Party (AICP), and later, United Communist Party of India. Towards the end, Dange got increasingly marginalised in the Indian Communist movement. He was also a well-known writer and was the founder of Socialist the first socialist weekly in India. Dange played an important role in the formation of Maharashtra state.

Muzaffar Ahmad (Bengali: ??????‌?? ????) (5 August 1889 – 18 December 1973) was a noted Bengali politician, journalist and communist activist, popularly known as "Kakababu". In 1918, he was appointed joint secretary of "Bangio musalman sahitya Samiti". In 1920, along with Kazi Nazrul Islam he started a new magazine, Navayug. Later, when another magazine, Dhumketu was launched by Nazrul in 1922, he contributed to it using the pseudonym "Dvaipayana".

Malayapuram Singaravelu Chettiar (18 February 1860 – 11 February 1946), also known as M. Singaravelu and Singaravelar, was a pioneer in more than one field in India. In 1918, he founded the first trade union in India. On 1 May 1923 he organised the first ever celebration of May Day in the country. Singaravelar was a major leader of the Indian independence movement, initially under the leadership of Gandhi, but later, joining the budding communist movement. In 1925, he became one of the founding fathers of the Communist Party of India; and chaired its inaugural convention in Kanpur. Though the British Government arrested him along with other leaders on charges of conspiring to wage war against the Crown, he was set free, soon after, on account of his failing health. Singaravelar was also a path-breaking social reformer who in his early life took to Buddhism, seeing it as a weapon against the evil of untouchability, which was particularly severe in the 19th-century India. He was also in the forefront of Self respect movement, in the Madras Presidency that fought for equal rights for backward castes.