Which of the following statements relating to public choice is true? a. A low voter turnout may result when voters perceive that the marginal cost of voting exceeds its marginal benefit. b. If the marginal cost of voting exceeds its marginal benefit, the vote is unimportant. c. Special-interest groups always cause the will of a majority to be imposed on a minority. d. All of the above are true.

Option A: A low voter turnout may result when voters perceive that the marginal cost of voting exceeds its marginal benefit. In this statement, "marginal cost of voting" refers to the effort, time, or any other resource a voter has to spend in order to vote. On the other hand, "marginal benefit" refers to the potential gain a voter perceives from voting, such as electing their preferred candidate or influencing a policy decision. This statement is suggesting that if a voter perceives the cost (effort, time, etc.) of voting to be greater than the potential benefit (influence, electing the preferred candidate, etc.), the voter may choose not to vote. In such cases, low voter turnout may result from individuals' calculation that voting is not worth the costs. This statement seems reasonable, as low voter turnout can indeed occur when individuals perceive the marginal cost of voting to be higher than its marginal benefit.

Option B: If the marginal cost of voting exceeds its marginal benefit, the vote is unimportant. This statement suggests that if a voter believes that the cost of voting is higher than the potential benefit of voting, then the vote is unimportant. However, this statement is not necessarily true. Although a voter may perceive that the marginal cost of voting is higher than its marginal benefit, it does not imply that the vote is unimportant. Voting may still be important, as it is a way to express one's preference and contribute to the decision-making process in a democratic system. Thus, this statement is not true.

Option C: Special-interest groups always cause the will of a majority to be imposed on a minority. This statement suggests that special-interest groups invariably result in the majority imposing their will on the minority. However, this statement is an overgeneralization as it assumes that special-interest groups always act this way. In reality, special-interest groups can influence policy decisions in various ways, and their impact is not always about imposing the majority's will on the minority. They can also protect minority interests, advocate for specific policies, or even work on behalf of a broader public interest. Therefore, this statement is not true.

Option D: All of the above are true. Since we have already established that Options B and C are not true, Option D cannot be true either.

Based on our analysis in Steps 1-4, we can conclude that the correct statement is: Option A: A low voter turnout may result when voters perceive that the marginal cost of voting exceeds its marginal benefit.