Professor Knight is famous for his theory of

Rent
Profit
Population
Wages

Professor Frank Knight is famous for his theory of profit. He argued that profit is a residual income that arises from uncertainty and entrepreneurship. In other words, profit is the reward that entrepreneurs receive for taking on the risk of starting and running a business.

Rent is a payment made to the owner of a factor of production, such as land or capital. Profit is a payment made to the owner of a business, regardless of the factors of production that are used.

Population is the total number of people in a given area. Wages are the payments made to workers for their labor.

In conclusion, Professor Knight is famous for his theory of profit. He argued that profit is a residual income that arises from uncertainty and entrepreneurship.