Q. Who authored the influential book "Hindutva: Who is a Hindu?" during imprisonment in the Cellular Jail, Andaman Islands?
Answer: Vinayak Damodar Savarkar
Notes: Vinayak Damodar Savarkar wrote "Hindutva: Who is a Hindu?" in 1923 while imprisoned in the Cellular Jail, Andaman Islands. The work defined Hindutva and profoundly influenced Hindu nationalist ideology. The Cellular Jail is now a national memorial of India’s freedom struggle.