The correct answer is "1 only" because Arasavalli is known for its Sun temple, which is dedicated to the Sun God and is one of the oldest in India, reflecting ancient architectural styles and religious practices. In contrast, Amarkantak is primarily known as a pilgrimage site associated with the Narmada River and its source, and Omkareshwar is more famous for its Shiva temple rather than any Sun temple. Understanding the significance of specific temples within Indian architecture and history is crucial for UPSC Prelims as it reflects cultural heritage and regional diversity in religious practices.