Explanation:

- Family: This represents households that consume goods and services and provide labor and capital to firms.

- Firm: Refers to businesses that produce goods and services and demand labor, capital, and resources from households and government.

- Government: Engages in purchasing goods and services, collecting taxes, and redistributing income and resources.

- All of these: In the three-sector model, the economy is often described as consisting of three major players: households (families), firms, and the government, all interacting within the economic system.

Therefore, the correct answer is:

- Option 4: All of these