More than 4000 years ago, the Akkadians created the first official postal system. Are there any similarities to our postal system? How could the sender make sure the mail got to the right person?

One drawback of voluntary trade is that it a.requires two groups to use a common language b.can make one group dependent upon another for necessary goods c.doesn't occur unless there is a shortage of goods for at least one group d.forces groups to rely on themselves to produce all the goods they need