which of the following statements is correct

a. other things held constant, the more debt a firm uses, the higher its operating margin will be

b. debt management ratios show the exent to which a fim's managers are attempting to magnify returns on owners capital through the use of financial leverage

c. other things held constnat, the higher a firm's total debt to total capital ratio, the higher its time-interest-earned (TIE) ratio will be

d. debt managemetn ratios show the extent to which a firm's managers are attempting to reduce risk throught the use of financial leverage. the higher the total-debt-to-total-capital ratio, the lower the risk