Explanation:

Revenue-backed non-sovereign government bonds are typically issued to finance specific projects (e.g., toll roads, hospitals, or sports arenas). Unlike general obligation bonds, which rely on broader tax revenues, revenue bonds depend on the income generated by the project itself. Therefore, a critical credit measure for such bonds is the debt-service-coverage (DSC) ratio, which assesses the project's ability to generate sufficient revenue to cover debt payments (principal and interest) after operating expenses.

• Option A (Per capita income) is incorrect because it is more relevant for sovereign bonds or general obligation bonds, where the broader economic health of the jurisdiction is a key consideration.
• Option B (Breadth of the tax base) is also incorrect for the same reason, as it pertains to general obligation bonds rather than revenue-backed bonds.

Thus, the correct answer is C, as the DSC ratio is a direct and essential metric for evaluating the creditworthiness of revenue-backed non-sovereign government bonds.