Explanation:

The historic Lahore Session of the Indian National Congress, held in December 1929 under the presidency of Jawaharlal Nehru, was where the resolution for 'Poorna Swaraj' (complete self-rule or independence) was formally adopted. This declaration marked a pivotal shift in the Congress's objective from dominion status to full independence. Calcutta hosted earlier significant sessions, but not the 'Poorna Swaraj' resolution. Delhi was a political center but not the site of this specific resolution. The Karachi Session of 1931 adopted resolutions on Fundamental Rights, not 'Poorna Swaraj'.