Difference between a command economy and a centrally directed economy.

Market economies and command economies occupy two polar extremes in the organization of economic activity. The primary differences lie in the division of labor or factors of production and the mechanisms that determine prices. The activity in a market economy is unplanned; it is not organized by any central authority but is determined by the supply and demand of goods and services. The United States, England, and Japan are all examples of market economies. Alternatively, a command economy is organized by a centralized government which owns most, if not all businesses, and whose officials direct all the factors of production. China, North Korea, and the former Soviet Union are all examples of command economies. In reality, all economies blend some combination of market and command economies.

b.provides a written record of the transaction

explanation:

the addition to geographic boundaries that might have  kept the people of the huang river civilization from traveling to far distance region is that they had learned about the other river valley civilizations but feared contact would bring invasion.

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