The correct answer is: a) Tawang
Tawang district is located in the western part of Arunachal Pradesh, India. It is the largest district in the state, with a population of over 100,000 people. The majority of the population in Tawang district is from the Monpa tribe, which is a scheduled tribe. The Monpa people are a Buddhist people who have lived in the Tawang region for centuries. They are known for their unique culture and traditions.
The other options are incorrect because they do not have a particularly high concentration of ST population. East Kameng district has a population of over 300,000 people, but only a small percentage of the population is from ST groups. Lohit district has a population of over 200,000 people, and Changlang district has a population of over 100,000 people. Both of these districts have a higher percentage of ST population than East Kameng district, but they still do not have a particularly high concentration of ST population.
In conclusion, the correct answer to the question “Which district of Arunachal Pradesh has a particularly high concentration of ST population?” is a) Tawang.