Answer:
Untouchables - Considered subhuman, did worst possible work.
Untouchables exist outside the caste system of the Hindu religion because they are considered so low that some think them subhuman. As a result they are regularly subjected to abuse but there have been efforts to change their situation in recent years.
Brahmin - Priests and learned people.
This is the highest caste/ verna and consists of Priests, Advisors and learned people.
Shudra - Peasants and laborers
This is the lowest/ fourth caste and as seen, consists of Peasants and laborers. They do the menial work.
Vaishya - Farmers and merchants
This is the third highest caste/ verna. Consists of Farmers, traders and merchants.