When did the All India Congress formalise the demand for ‘Purna Swaraj’ or full independence for India?

Correct option is B

The correct answer is (b) At its Lahore Session in 1929.
 The demand for ‘Purna Swaraj’ or full independence for India was formalized at the Lahore Session of the Indian National Congress held in December 1929.
 The session was presided over by Jawaharlal Nehru.
 The Congress passed the historic 'Purna Swaraj' resolution, declaring that the goal of the Indian National Congress was complete independence from British rule.
 January 26, 1930, was declared as 'Independence Day,' and the Congress asked the people of India to observe it by taking a pledge of complete independence.
 This resolution marked a significant shift in the Indian freedom struggle, moving from the demand for dominion status to the demand for full sovereignty.
 The Lahore Session also witnessed the hoisting of the tricolor flag of India by Jawaharlal Nehru on the banks of the Ravi River, symbolizing the resolve for independence.