The citizens of the united states live and work in a
a. closed economy
b. command economy
c. mixed market economy
d. pure market economy

The correct answer is C.

The economic system in the US is a mixed market economy. The interactions of economic agents occurring in the markets, determine the amounts produced of goods and services, their market prices and the market prices of the different factors of production. Anyway, markets are subject to certain rules established by the economic authorities, in case that the outcomes reached by the free functioning of markets are not consider fair for all the individuals who constitute a society.

The existence of certain degree of goverment interventionism in the economy to regulate markets, rules out the options of a pure market economy and of a pure centrally-planed or command economy. Moreover, the US cannot have a closed economy, because economic relationships are established with foreign countries.