The correct answer is option 4: the North-eastern region. Mongoloids, which refers to people with physical features that are characteristic of East Asian populations, are found predominantly in the North-eastern region of India. This region, also known as the Seven Sister States, consists of Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, and Tripura. It is important to note that while there may be some individuals with Mongoloid features in other regions of India, they are more concentrated in the North-eastern region. The Southern region, South-central region, and North-western region do not have a significant presence of Mongoloid ethnic groups. Overall, the North-eastern region is recognized for its cultural and ethnic diversity.