以下物质不具有光敏性的是()

A．石蜡

B．焦油

C．某些香料

D．洗涤剂中的荧光增白剂

The company has a target capital structure of 40 percent debt and 60 percent equity. Bonds pay 10 percent coupon (semi-annual payout ), mature in 20 years, and sell for $849.54. The company stock beta is 1.2. Risk-free rate is 10 percent, and market risk premium is 5 percent. The company is a constant growth firm that just paid a dividend of $2.00, sells for $27.00 per share, and has a growth rate of 8 percent. The company’s marginal tax rate is 40 percent. The after-tax cost of debt is:（）

A. 8.0%.

B. 9.1%.

C. 7.2%.