The correct answer is (a).
As capitalist accumulation progresses, the productivity of labor increases and workers’ standard of living decreases. Sounds paradoxical, right? In vol. 1, ch. 25 of Capital, Marx explains the cycle of accumulation. As firms grow, they buy more equipment, which requires more workers to run. However, due to technological progress, each new generation of equipment requires fewer workers to set in motion. So the growth of a firm is generally an increase in the ratio of machines (fixed capital) to human labor (variable capital). As firms grow, they tend to reduce their labor force–a trend recognized even by bourgeois economists. This is the process that we’ve seen with automation of the manufacturing sector. As we’ve seen over the past four decades, massive increases in industrial productivity result in unemployment, underemployment, and a lower standard of living for the working class.
Marx wrote this section of Capital to refute the idea that the growth of business is good for workers–an absurd claim still made by many mainstream economists.