D. Member nations combine and coordinate their economies.
Explanation:
The European Union is a single common market with the same rules, where competitors from other EU countries compete under the same conditions with a local member´s firms. The EU, and that´s the work of its executive branch the European Commission, has uniform norms and standards; all its members must follow similar macroeconomic, fiscal and trade policies.
The fact that US citizens have a high per capita income (per capita = per person) allows them to consume a disproportionately large amount of products compared to the rest of the world. So I think the answer is B.
