When We Say That the European Union Has a Single

When we say that the European Union has a single market, we are saying that

A) its members trade exclusively with one another.
B) the prices of goods and services are set by the European Union, rather than the free market system.
C) all member states use a common currency.
D) there are few barriers to the free movement of goods, services, people, and capital among member states.
E) there are few barriers to the free movement of goods and services between members states, but there are significant barriers concerning the movement of capital and people.