Which One of the Following Statements Is Correct? Assume the Pretax

Which one of the following statements is correct? Assume the pretax cost of debt is less than the cost of equity.

A) A firm may change its capital structure if the government changes its tax policies.
B) A decrease in the dividend growth rate increases the cost of equity.
C) A decrease in the systematic risk of a firm will increase the firm's cost of capital.
D) A decrease in a firm's debt-equity ratio will decrease the firm's cost of capital.
E) The cost of preferred stock decreases when the tax rate increases.