A goal of the EU (European Union) was to make trade easier & reduce the cost of trading for all EU nations. How were they able to accomplish that?

A. by controlling the all of the nations governments
B. by having them use the same type of currency (money)
C. by paying for all taxes and tariffs

D. by creating a single market with no barriers for trade, such as tariffs or quotas, and by implementing common regulations and standards for businesses and products.