What is the agreement established to lower trade barriers among certain European countries, which is now part of the EU?

The correct answer is the concept of a common market, which refers to an agreement that facilitates the free movement of goods, services, capital, and labor between member countries. In a common market, not only are tariffs and quotas eliminated, but there is also a commitment to maintaining similar standards and regulations across participating countries, which enhances economic integration.

Historically, the idea of a common market was a fundamental component in the formation of what is now the European Union. It involves deeper integration than just a free trade area because it also includes the removal of restrictions on the movement of factors of production. This has allowed member countries to operate as a single market, increasing trade efficiency and economic cooperation among the nations involved.

While terms like "single market" may come into play as well, they are often used subsequently to describe a more integrated form of the common market. The single market concept elaborates on the ideas of a common market, emphasizing the importance of standardized regulations and policies to support seamless market operations among EU member states.

In contrast, options like "trade union" and "European trade agreement" do not specifically capture the framework of economic integration in the same way. A trade union mainly refers to an organization that represents workers in negotiations with employers, while a