Autocracies could survive the threat of a revolution if they could credibly commit to current and future redistribution of the resources. However: a. commitment to future policies is only possible in democracies. b. such promises are not credible as the elte is likely to renege on them once conditions are more favorable and the threat of a revolution is less strong. c. such promises are always too costly for the elite which is therefore going to prefer to demcoratize. d. such prmises are not credible as the elite is likely to redistribute too much and therefore will change its mind in the future