The correct answer is Optimum. An optimum capital structure refers to the specific mix of debt and equity financing that minimizes a company's weighted average cost of capital (WACC) and maximizes its market value. Achieving an optimum capital structure is a primary goal of financial management, as it allows the firm to raise capital at the lowest possible cost, thereby enhancing shareholder wealth. This balance considers the trade-off between the tax benefits of debt and the increased financial risk associated with higher leverage.
Preference share (A) refers to a specific type of equity security that pays fixed dividends, not a type of capital structure. Equity (C) represents ownership capital, and Debt (D) represents borrowed capital; both are components of a capital structure, but neither alone describes the ideal combination. The term 'optimum' specifically denotes the most efficient and value-maximizing blend of these components. Therefore, an optimum capital structure is the ideal combination that helps attain the marginal goal of maximizing firm value.