Adam Smith taught that individual buyers and sellers who act in their own self interest frequently promote society's interest. What assumption is needed for society's interest to be promoted?

All of the above

Explanation:

In a market economy, most businesses have most of the resources available to them such as labor, land, and capital. They make use of voluntary decisions, that are made in their own self-interest, to achieve the highest personal benefit from various marketplace activities and transactions.

Self-interest dominate in capitalist economies where goods and services are exchanged with ease. These forces are responsible for driving the supply and demand for goods and services as well as the value of goods and services.

Adam Smith was one of the first economists to explain how self-interest and rational self-interest in a free-market economy can result to the entire economic well-being.