Correct Answer: Labour

Solution : The correct option is Labour.

The worth of a good is defined by the quantity of socially necessary labour time needed to manufacture it, in accordance with Karl Marx's theory of labor value. In other words, a product's value is determined by the amount of labour used to produce it.  In a capitalist society, workers, according to Marx, sell their labour force to capitalists in exchange for a wage. Then, the capitalist owns the means of production and appropriates the excess value produced by the workers' labor. According to Marx, the capitalist's source of profit is this excess value.