Answer:
The development that would most likely reflect Karl Marx's belief in the economic system that he predicted would be:
A socialist revolution led by the proletariat (working class)
Karl Marx predicted that capitalism would eventually lead to class struggle between the bourgeoisie (owners of the means of production) and the proletariat (working class). He believed that this struggle would intensify, leading to a socialist revolution where the proletariat would overthrow the bourgeoisie and establish a classless society where the means of production are collectively owned (socialism). Marx's predictions included the eventual transition from socialism to communism, where private property would be abolished and society would operate based on the principle of "from each according to his ability, to each according to his needs."
Therefore, the development that aligns most closely with Marx's predictions and beliefs in the economic system would be a socialist revolution led by the proletariat, aiming to establish socialism and eventually communism.