A "closed economy" is an economy in which

1. A closed economy is defined as an economy that does not engage in international trade; it has no exports or imports with the rest of the world. 2. Option (A) is incorrect: Control over the money supply is a function of monetary policy and can exist in both open and closed economies. 3. Option (B) is incorrect: Deficit financing is a method of funding government spending and can occur in both open and closed economies. 4. Option (C) is incorrect: An economy with only exports would still be an open economy, interacting with other countries, just not importing. 5. Option (D) correctly defines a closed economy as one where neither exports nor imports take place.