Choice "C" is correct. The optimal capitalization for an organization usually can be determined by the lowest total weighted-average cost of capital (WACC). Capitalization at WACC serves to maximize shareholder's equity.
Choice "b" is incorrect. The degree of financial leverage relates to the risk assumed by a firm using fixed debt service costs to finance operations not comprehensively to capital structure.
Choice "d" is incorrect. The degree of total leverage relates the risk assumed by a firm using a combination of both debt services costs to finance operations and fixed costs to operate the business, not comprehensively to capital structure.
Choice "a" is incorrect. The intersection of the marginal cost of capital and the marginal efficiency of investment does not indicate optimal capitalization.