Which statement is true regarding debt in a capital structure?

In the context of capital structure, the statement that all debt must be repaid before any equity holder receives payment in liquidation is true. This reflects the priority of claims in the event of a company's liquidation. When a company is liquidated, creditors—those who hold debt instruments—must be paid first before any distributions can be made to equity holders. This establishes a hierarchy of claims, where debt holders have a contractual right to receive their payments before any residual value can be distributed to shareholders.

The other choices introduce concepts that do not accurately reflect the nature of debt in relation to equity. Debt does not inherently guarantee returns to shareholders; such returns are contingent on the company's financial performance. Furthermore, while it is common for debt to have a lower cost of capital compared to equity, this is not universally true as various factors such as market conditions and the specific risk profile of a company can influence the cost of capital. Finally, debt investors typically do not have voting rights in the company; those rights are generally reserved for equity holders. Thus, option A stands out as the accurate statement regarding the treatment of debt in a company's capital structure.