The correct answer for the question is option 1, Indigo. Champaran Satyagraha was a significant event in the Indian freedom struggle led by Mahatma Gandhi in 1917. The movement was against the forced indigo cultivation by British planters in Champaran, Bihar. Indigo was a cash crop used for dye production and the planters exploited the local farmers, compelling them to grow indigo on their lands. The farmers were forced to bear the burden of excessive taxes and unfair treatment. Mahatma Gandhi, along with a team of lawyers and social workers, organized protests and advocated for the rights of the farmers. This led to a successful resolution of the issue, and the Champaran Satyagraha became a crucial moment in India`s fight for independence.