The correct answer is option-2 Prayag. Harshavardhana, who was a prominent emperor of ancient India, organized his religious assembly or Mahakumbha at Prayag. Prayag, also known as Allahabad, is a city in present-day Uttar Pradesh, India. It holds great religious significance and is considered a holy city by Hindus. Prayag is situated at the confluence of the rivers Ganga, Yamuna, and Sarasvati, which is believed to be a sacred location in Hindu mythology. The Mahakumbha is a major religious gathering held every 12 years at Prayag, attracting millions of pilgrims from all over the country. Harshavardhana`s decision to organize his religious assembly at Prayag showcases his devotion to the Hindu religion and his desire to foster religious harmony and unity among his subjects.