When we look at the differences between a command economy and a mixed market economy, the most significant factor is the degree of government control. Therefore, the answer is b) a greater degree of government control over production and investment.
A command economy is characterized by the government making all major economic decisions. This includes determining what goods and services are produced, how they are distributed, and what prices are set. In contrast, a mixed market economy allows for both private enterprise and government involvement, leading to a more decentralized decision-making process.
In a command economy, the government controls resources and allocates them according to a national plan, which often results in limited private ownership. On the other hand, a mixed market economy embraces private ownership and allows market forces to play a significant role in economic decisions.
Thus, while command economies may also face some level of income inequality or other issues, the defining feature that sets them apart from mixed market economies is the extent of government control over production and investment.