Explanation:

The **Purna Swaraj (Complete Independence) declaration** was a landmark event in the Indian independence movement. It was formally adopted as a resolution by the Indian National Congress at its Lahore Session in December 1929, presided over by Jawaharlal Nehru. Following this, the Congress declared that January 26, **1930**, would be celebrated as 'Purna Swaraj Day' or 'Independence Day' across India, and a pledge of independence was read out. This date was chosen to symbolize the nation's resolve for complete freedom from British rule. Option C is correct. The year 1928 (Option A) saw the Simon Commission's arrival and the Nehru Report. The Lahore Session where the resolution was passed occurred in late 1929 (Option B), but the *declaration* and celebration of Purna Swaraj Day took place in 1930. The year 1931 (Option D) saw the Gandhi-Irwin Pact and the Second Round Table Conference, which occurred after the Purna Swaraj declaration.