a. The benefits are collective and they enjoy the payoff even if they have not helped to produce them by voting.
b. The benefits are individual, but since governments do not provide many tangible benefits, the costs of voting outweigh the benefits.
c. Votes do not really matter because politicians can manipulate the public into believing whatever they want.
d. The system of separated institutions sharing powers provides more influence to the unelected branches of the government, such as the judiciary and the bureaucracy.