According to Karl Marx, what dialectic contradiction lies at the heart of capitalism?

A) Capitalists need to exploit workers for profit; workers want to profit from their work.
B) Capitalism embraces the greed opposed by the protestant ethic.
C) Capitalism needs stability; but change is inevitable.
D) Capitalism is based on class conflict; but classes are cooperative by nature.

Marx believed that the fundamental contradiction of capitalism lies in the relationship between capitalists and workers. Capitalists seek to maximize profits by extracting as much labor as possible from workers while paying them the bare minimum necessary for their survival. Workers, on the other hand, want to receive higher wages for their labor and to have more control over their work. This leads to a constant struggle between the two classes, and Marx believed that this struggle would eventually lead to the overthrow of the capitalist system.