The correct answer is: a) Krishak Sabha.
The Krishak Sabha was a peasant organization that played a role in mobilizing farmers in Assam during the colonial period. It was founded in 1929 by a group of farmers who were concerned about the low prices they were receiving for their crops. The Krishak Sabha organized protests and strikes, and it also lobbied the government for better prices for farmers.
The Asom Jatiya Mahasabha was a political party that was founded in 1920. It was not a peasant organization, but it did have some support from farmers. The All India Trade Union Congress is a trade union federation that was founded in 1920. It is not a peasant organization, and it does not have any members in Assam. The Assam Chah Mazdoor Sangha is a trade union that represents tea workers in Assam. It is not a peasant organization, and it does not have any members who are not tea workers.
The Krishak Sabha was the most important peasant organization in Assam during the colonial period. It played a significant role in mobilizing farmers and improving their conditions.