In medieval India, the terms Khud kashta and Pahi Kashta were used to refer to peasants.

Explanation:
In medieval India, the society was divided into various social groups based on occupation and status. The term Khud kashta and Pahi Kashta specifically referred to the peasant class. Here is a detailed explanation of why the correct answer is option 'B' - peasants.

1. Peasants as the backbone of the agrarian society:
- Peasants formed the majority of the population in medieval India and played a crucial role in the agrarian economy.
- They were primarily involved in agricultural activities, cultivating land and producing food crops.
- The agricultural produce of the peasants sustained the entire society, including the ruling class, artisans, and merchants.

2. Khud kashta and Pahi Kashta:
- The terms Khud kashta and Pahi Kashta were used to classify different categories of peasants based on the extent of land they cultivated and the proportion of the produce they retained.
- Khud kashta referred to peasants who cultivated land using their own resources and retained the entire produce for themselves.
- Pahi Kashta, on the other hand, referred to peasants who cultivated land owned by others, such as the landlords or the ruling elites.
- Pahi Kashta peasants had to give a portion of their produce as rent or revenue to the landowners.
- The term "Kashta" signifies the toil or labor of the peasants, indicating their hard work and contribution to the agricultural sector.

3. Importance of peasants in the feudal society:
- Peasants formed the foundation of the feudal society, as they were responsible for producing food and sustaining the entire population.
- The ruling elites, including the kings and feudal lords, heavily relied on the agricultural surplus generated by the peasants.
- The surplus produce ensured the availability of food for the ruling class, artisans, merchants, and other sections of society.
- The peasants' labor and agricultural productivity were critical for maintaining the stability and functioning of the medieval Indian society.

In conclusion, the terms Khud kashta and Pahi Kashta were used to classify and refer to peasants in medieval India. These terms highlighted the different categories of peasants based on land ownership and the proportion of produce retained. Peasants played a vital role in the agrarian society, producing food crops and sustaining the entire population.