The correct answer is a) Churachandpur.
Churachandpur is a district in the Indian state of Manipur. It is located in the south-western part of the state and shares a border with Nagaland. The district is named after Churachand Singh, the first king of Manipur.
Churachandpur is a hilly district with a population of over 400,000 people. The main language spoken in the district is Meitei. The district is home to a number of different ethnic groups, including the Meiteis, Kukis, Nagas, and Mizos.
The main economic activities in Churachandpur are agriculture, forestry, and tourism. The district is also home to a number of industries, including the production of handloom textiles, bamboo products, and handicrafts.
Churachandpur is a beautiful district with a rich history and culture. It is a popular tourist destination, known for its natural beauty, its cultural heritage, and its friendly people.
Option b, Ukhrul, is also a district in Manipur that shares a border with Nagaland. However, it is not the district that shares the longest border with Nagaland.
Option c, Peren, is a district in Nagaland. It does not share a border with Manipur.
Option d, Senapati, is a district in Manipur. It shares a border with Nagaland, but it is not the district that shares the longest border with Nagaland.