Which Aspect of Marx's Theory Results in the Critique That

Which aspect of Marx's theory results in the critique that Marx underrated the ability of individuals to adjust to inequality?

A) Marx underestimated the proletariat and its willingness to engage in a long historical process rather than their day-to-day concerns.
B) Marx underestimated the strength and adaptability of capitalists.
C) The bourgeoisie did not provide for the proletariat the intended revolutionary impetus.
D) Marx was a good sociologist but not a good judge of human nature.