Correct Answer : Option (D) - Every 12 years at 4 locations
It is the world's largest peaceful gathering of people. Ardh Kumbh is held every six years, while the Maha Kumbh Mela comes after 12 years. The Maha Kumbh is held at Prayagraj while Ardh Kumbh is organized on a rotational basis in the four riverside cities of Haridwar, Prayagraj, Nasik and Ujjain.