Explanation: Purvanchal is a geographical region in eastern India that comprises a series of hill ranges running parallel to the Himalayas. The term "Purvanchal" translates to "eastern range" in Sanskrit, indicating its location in the eastern part of the country. This region is an important part of the eastern extension of the Himalayan range and includes several significant hill ranges.
The Naga Hills, located in the northeastern part of India, are a prominent feature of the Purvanchal region. They are characterized by their rugged terrain and are an integral part of the eastern Himalayan range. The Naga Hills are not only significant for their geographical features but also for their cultural and ecological importance. They are home to diverse flora and fauna and are inhabited by various indigenous communities.
In contrast, the other options provided do not belong to the Purvanchal region. Kotli Dun is a valley located in the state of Uttarakhand, situated in the Garhwal Himalayas. It is part of the Western Himalayas and not the eastern extension of the Himalayan range. The Dhaula Dhar range, located in Himachal Pradesh, is also part of the Western Himalayas and does not belong to the Purvanchal region.
Understanding the geographical layout of India's physiographic regions is crucial for comprehending the country's diverse topography. The Purvanchal region, with its significant hill ranges like the Naga Hills, plays a vital role in the eastern part of the country, contributing to its unique geographical and ecological characteristics.