Question

A key principle of the economic theory of communism is

Answer 1

A key principle of the economic theory of communism is the systematic redistribution of wealth from those who worked to earn it to those who don't have as much of it.
Hope that helped =)

Answer 2

Communism is not about a redistribution of wealth. Communism argues that wealth is unequally distributed in the first place because capitalism is inherently unfair, and that redistributing wealth (by taking from rich people and giving to poor people) would never solve the problem in the long term. Communism therefore seeks to eliminate capitalism altogether by eliminating markets, by giving the government control of the means of production (like factories and farms), and by distributing goods (like food and gasoline) to people according to need. The goal is to eliminate economic classes by eliminating need, so that there's no need to redistribute wealth, since everyone would be in an equal condition of prosperity. In practice, however, this has never really worked out.