Concept:Public ownership of productive factors means the community or state controls the resources used to produce goods and services.
Explanation:Under socialism, the government or society collectively owns and manages key productive resources such as land, factories, and capital.
This is opposite to capitalism, where private individuals own these factors.
Feudalism is based on land ownership by lords, while a mixed economy combines private and public ownership.
Therefore, public ownership of productive factors is the defining feature of socialism.
Answer:A. Socialism