Final answer:
During the dictatorship of the proletariat in Marx's proposed transition from capitalism to communism, a factory owner would have their factory and property taken over by the government.
Step-by-step explanation:
During the transition from capitalism to communism as proposed by Marx, the step in which a factory owner would have their factory and property taken over by the government is during the dictatorship of the proletariat. This is a temporary period when the working class takes control of the state and implements policies to prepare for communism. In this phase, the government may seize privately held technologies and assert control over the means of production, including factories.