The correct answer is option 3, B.R. Ambedkar. He was the one who organized the All India Scheduled Castes Federation.

Option 1, Jyotiba Phule was a social reformer in Maharashtra who worked for the rights of lower caste and women. While he made significant contributions towards social equality, he did not organize the All India Scheduled Castes Federation.

Option 2, Periyar, also known as E.V. Ramasamy, was a social activist from Tamil Nadu. He fought against caste discrimination and advocated for social justice. However, he was not the organizer of the All India Scheduled Castes Federation.

Option 4, M.K. Karunanidhi, was a prominent politician from Tamil Nadu. He served as the Chief Minister of the state multiple times. However, he was not involved in organizing the All India Scheduled Castes Federation.

Therefore, from the given options, it is clear that B.R. Ambedkar was the one who organized the All India Scheduled Castes Federation.