These goods and services are referred to as "public goods and services". These services are available to all citizens and visitors of the US, and are paid for with tax revenue.
Silk Road. (the worlds oldest trade route)
Answer: Silk Road
Explanation:
That was the easiest question I answered all day.
It would be between increased population, a steady stream of agricultural production, and technological advancements. As for the most important one of those three; that would be agricultural production.
