Final answer:
A single individual with a low income would benefit the least from an income-shifting strategy due to being in a lower tax bracket already, whereas high-income earners and families with multiple income earners have more to gain due to progressive taxation.
Step-by-step explanation:
Income-shifting strategies are typically used to reduce tax liabilities by moving income from higher tax brackets to lower ones. Of the options provided, C) A single individual with a low income would likely benefit the least from income-shifting strategies. This is primarily because such individuals are already in the lower tax brackets and the progressive nature of the tax system would not offer them significant benefits through income shifting.
Progressive tax systems impose higher tax rates on higher income brackets, which means that high-income individuals and families with multiple earners would have more potential for tax savings through income shifting. However, for low-income individuals, especially if they are single, the marginal gains would be minimal since their income is not subjected to substantially higher tax rates.
In contrast, a high-income individual or a family with multiple income earners often find themselves in higher tax brackets where the marginal tax rate increases with the level of income, creating a stronger incentive and higher potential benefit from income shifting.