The largest district in Mizoram by population is:

Aizawl
Champhai
Lunglei
Kolasib

The correct answer is: a) Aizawl.

Aizawl is the capital and largest district of Mizoram, India. It is located in the central part of the state and has a population of over 250,000 people. The district is known for its beautiful scenery, including its many hills and valleys. It is also home to a number of important cultural and historical sites, such as the Aizawl Palace and the Vanapa Hall.

Champhai is the second largest district in Mizoram, with a population of over 150,000 people. It is located in the southern part of the state and is known for its beautiful beaches and its diverse wildlife. The district is also home to a number of important cultural and historical sites, such as the Champhai Palace and the Champhai Museum.

Lunglei is the third largest district in Mizoram, with a population of over 100,000 people. It is located in the central part of the state and is known for its beautiful scenery, including its many hills and valleys. The district is also home to a number of important cultural and historical sites, such as the Lunglei Palace and the Lunglei Museum.

Kolasib is the fourth largest district in Mizoram, with a population of over 50,000 people. It is located in the eastern part of the state and is known for its beautiful scenery, including its many hills and valleys. The district is also home to a number of important cultural and historical sites, such as the Kolasib Palace and the Kolasib Museum.