Maulana Abul Kalam Azad served as the President of the Indian National Congress for six consecutive years from 1940 to 1946. This was the longest continuous tenure in the pre-independence era. His presidency coincided with critical events like the Quit India Movement and the negotiations for the transfer of power, during which he remained a steadfast voice for a secular, unified India. ANSWER: (C) Abul Kalam Azad