Think about trade in early empires versus trade today.

The correct answer to this open question is the following.

Trade in the early empires represented the opportunity to exchange products that ancient people needed with other towns or city-states, as was the case of Sumeria. City-states such as Kish, Uruk or Ur traded between them and years later they reached as far as the Indus Valley Civilization. Years later, the Silk Road represented the way to trade in those far lands from China to Africa and some parts of Europe.

Modern-day trade is more complex because other countries have their own rules and regulations on trade, imports, and exports. The international c}urreny is the American dollar. To eliminate barriers that impede free trade, countries had come up with the idea of free trade agreements such as the North American Free Trade Agreement signed by México, the United States, and Canada.

the berlin blockade was an international crisis that arose from an attempt by the soviet union, in 1948–49, to force the western allied powers (the united states, the united kingdom, and france) to abandon their post-world war ii jurisdictions in west berlin. in march 1948 the allied powers decided to unite their different occupation zones of germany into a single economic unit. in protest, the soviet representative withdrew from the allied control council. coincident with the introduction of a new deutsche mark in west berlin (as throughout west germany), which the soviets regarded as a violation of agreements with the allies, the soviet occupation forces in eastern germany began a blockade of all rail, road, and water communications between berlin and the west. on june 24 the soviets announced that the four-power administration of berlin had ceased and that the allies no longer had any rights there.