The United States and the European Union Are Groups of Semi-Independent

The United States and the European Union are groups of semi-independent states that have come together under an agreement whereby resources can travel freely across borders and a common currency is in use. Which of the following statements best explains how this allows for the achievement of economies of scale?

A) Each state or country can now target larger markets and can thus earn more export revenue.
B) States and countries no longer have to worry about borders impeding trade.
C) Each state or country can adopt large-scale production techniques that allow lower per-unit costs of production.
D) The removal of trade borders and a common currency enhances trade between member states.