Explanation:

- Option 1: Supply only

- Incorrect. Supply impacts price, but alone it doesn't determine equilibrium.

- Option 2: The Government

- Incorrect. Governments can influence prices through regulations, but they do not establish market equilibrium.

- Option 3: Demand only

- Incorrect. Demand affects price, but solely it can't set the equilibrium.

- ? Option 4: Demand and supply

- Correct. Equilibrium price results from the interaction between demand and supply. It is the point where demand equals supply, leading to a stable pricing situation.