Answer: C. Must comply with EU regulations when doing business in the European Union only.
Explanation:
European Union tax and pollution laws are meant to bind only the area in the EU and not other areas. For instance, a Nebraska state law that is not law in other parts of the country only covers Nebraska and so can only be enforced there.
The same logic goes for the EU. Their laws are only applicable if you are in their area of control. This means that U.S. companies doing business in the EU must comply with EU regulations when doing business in the EU only.