According to the theory of "the race between education and technology," what factor is largely responsible for the increase in the real wages of college graduates (relative to the real wages of non-college workers) in recent decades? A.) A speeding-up of growth in firms' demand for highly educated workers. B.) A slowing-down of the growth of college attainment rates in the population. C.) The growing ability of robots and/or computer programs to perform tasks that had previously been performed by less-educated workers. D.) The loss of manufacturing jobs to China and other developing countries. E.) All of the above.