Champaran Satyagraha (1917) of Mahatma Gandhi was associated with:
The correct answer is option 'B' - Indigo farmers.

Explanation:
The Champaran Satyagraha was a significant event in India's freedom struggle and was led by Mahatma Gandhi in 1917. It took place in the Champaran district of Bihar, where the majority of farmers were forced to cultivate indigo by the British planters. This movement was a turning point in Gandhi's activism and marked the beginning of his experiments with nonviolent resistance.

Background:
During the British colonial rule, the indigo plant was extensively cultivated in the Champaran region. The British planters used exploitative methods to force the local farmers to cultivate indigo on a large scale. The farmers were forced to grow indigo on at least 3/20th of their land, which severely affected their livelihoods and economic conditions. The farmers were also subjected to numerous oppressive acts by the indigo planters, including extortion and forced labor.

Initiation of the Satyagraha:
Mahatma Gandhi was invited to Champaran by Raj Kumar Shukla, a local farmer who had suffered greatly under the exploitative indigo system. Gandhi arrived in Champaran on 10th April 1917 and soon began his investigations into the plight of the farmers. He organized meetings, listened to the grievances of the farmers, and collected evidence of the atrocities committed by the planters.

The Satyagraha:
Gandhi decided to launch a satyagraha (nonviolent resistance) to fight against the oppressive indigo system. He encouraged the farmers to refuse to grow indigo and organized mass protests and demonstrations. The British authorities initially tried to suppress the movement by arresting Gandhi and his associates, but they were unsuccessful in their attempts.

Negotiations and Reforms:
The Champaran Satyagraha gained significant attention and support from various sections of society. The British government was compelled to initiate negotiations with Gandhi. As a result of the negotiations, the Champaran Agrarian Act of 1918 was passed, which addressed the grievances of the farmers. The Act abolished the oppressive indigo system, reduced the rent for farmers, and provided them with some security of tenure.

Significance:
The Champaran Satyagraha was a landmark event as it marked the first major success of Mahatma Gandhi's nonviolent resistance strategy. It established the efficacy of satyagraha as a tool for social and political change. Furthermore, it brought national attention to the issues faced by the farmers and laid the foundation for future agrarian movements in India.

In conclusion, the Champaran Satyagraha led by Mahatma Gandhi in 1917 was primarily associated with the struggles of the indigo farmers in the Champaran district of Bihar. The movement aimed to address their grievances, abolish the oppressive indigo system, and secure their rights and livelihoods.