The correct options are
A mountainous terrain
B semi arid
Areas with low population density are those areas which contain less than 250 persons per sq. km which includes the states of Rajasthan, Himachal Pradesh, Uttaranchal, Chhattisgarh, Madhya Pradesh, Sikkim, Meghalaya, Manipur, Nagaland, and Arunachal Pradesh.
The Union Territories of Jammu and Kashmir, as well as the Andaman and Nicobar Islands, fall in this category. These areas are characterised by mountainous terrain, with semi-arid climates, which is why the population density is low here.