The correct answer is: Papum Pare.
Papum Pare is the most populous district in Arunachal Pradesh, with a population density of 102 people per square kilometer. It is located in the central part of the state and is home to the capital city of Itanagar. The district is also home to a number of other important towns and cities, including Naharlagun, Changlang, and Roing.
Lohit is the second most populous district in Arunachal Pradesh, with a population density of 60 people per square kilometer. It is located in the eastern part of the state and is home to the towns of Tezu and Namsai.
Kra Daadi is the third most populous district in Arunachal Pradesh, with a population density of 40 people per square kilometer. It is located in the northwestern part of the state and is home to the towns of Bomdila and Tawang.
Dibang Valley is the fourth most populous district in Arunachal Pradesh, with a population density of 20 people per square kilometer. It is located in the northeastern part of the state and is home to the towns of Anini and Roing.
The population density of a district is calculated by dividing the total population of the district by the area of the district. The population density of Papum Pare is higher than the population density of the other districts in Arunachal Pradesh because it is the most populous district.