The first all-India Communist Conference, which the CPI regards as its formal founding, was held on 26 December 1925 at:

The first all-India Communist Conference was held at Kanpur (Cawnpore) on 26 December 1925; the Communist Party of India (CPI) regards this as its formal founding.

About the conference:

It was organised by Satyabhakta, a journalist of Kanpur, and was held at the time of the Kanpur session of the Indian National Congress.

It was presided over by M. Singaravelu Chettiar of Madras.

It brought together various communist groups from different parts of India.

It decided to form an all-India party, the Communist Party of India, with its headquarters in Bombay.

• V. Ghate was its first general secretary.

Debate over the founding date:

• An earlier group of Indian communists had formed a party abroad in 1920.
• The CPI considers 1925 (Kanpur) as its founding year, while the CPI(M) considers the earlier date.

Early communist activities in India:

• The communists worked among industrial workers and peasants, and set up Workers' and Peasants' Parties in different provinces in the late 1920s.
• They led many strikes, especially in the textile mills of Bombay and the jute mills of Bengal.

Repression:

• The British government saw communism as a serious threat, and brought conspiracy cases against communist leaders.
• In the Meerut Conspiracy Case (1929-1933), 31 communist and trade union leaders, including some British communists, were tried; many were sentenced to long prison terms.
• The CPI was banned in 1934, and the ban was lifted in 1942.

About M. Singaravelu:

He was a pioneer of the labour and communist movement in south India, and organised the first May Day celebration in India in Madras (1923).

Why not the other options?

• ✗Bombay became the party's headquarters; Calcutta and Meerut were connected with other events.