Kushal Konwar, a young freedom fighter from Assam, was hanged for his role in:

Derailing a train carrying British troops
Attacking a police station
Organizing a mass protest
Distributing anti-British pamphlets

The correct answer is: a) Derailing a train carrying British troops.

Kushal Konwar was a young freedom fighter from Assam who was hanged by the British for his role in derailing a train carrying British troops. He was a member of the Indian National Army (INA), which was formed by Indian soldiers who had been captured by the Japanese during World War II. The INA fought against the British in India, and Konwar was one of the most prominent leaders of the INA in Assam.

Konwar was arrested by the British in 1945 and charged with treason. He was found guilty and sentenced to death. He was hanged in 1946, at the age of 23.

Konwar is remembered as a hero of the Indian independence movement. He is considered to be one of the most important figures in the history of Assam.

Here is a brief explanation of each option:

a) Derailing a train carrying British troops: This is the correct answer. Konwar was hanged for his role in derailing a train carrying British troops.
b) Attacking a police station: This is not the correct answer. Konwar was not involved in attacking a police station.
c) Organizing a mass protest: This is not the correct answer. Konwar was not involved in organizing a mass protest.
d) Distributing anti-British pamphlets: This is not the correct answer. Konwar was not involved in distributing anti-British pamphlets.