Explanation:

The Azad Hind Fauj, also known as the Indian National Army (INA), was formed during World War II to secure Indian independence with Japanese assistance:

- Option 1: Singapore - Correct. The Indian National Army was formed in Singapore with the assistance of the Japanese during World War II, initially by Mohan Singh and later re-organized by Subhas Chandra Bose.

- Option 2: Tokyo - While Japan played a role in aiding the INA, Tokyo was not the location of its formation.

- Option 3: Berlin - Subhas Chandra Bose sought Axis support in Berlin, but the INA was not formed there.

- Option 4: Rangoon - While the INA operated in Burma (Myanmar), it was not formed in Rangoon.

Option 1 (Singapore) is the correct choice