The first General Secretary of the Indian National Congress was A.O. Hume. The Indian National Congress was founded in 1885, and Allan Octavian Hume played a crucial role in its establishment. Hume was a British civil servant who saw the need for an organized political platform for Indians to voice their concerns and advocate for their rights. As the General Secretary, Hume was responsible for coordinating the activities of the Indian National Congress and ensuring its smooth functioning. Although all the other options mentioned (Dadabhai Naoroji, Ferozeshah Mehta, Badruddin Tyabji) were prominent leaders associated with the Indian National Congress, they did not hold the position of General Secretary. Therefore, the correct answer is option 2, A.O. Hume.