All Else Constant, an Increase in a Firm's Cost of Debt

All else constant, an increase in a firm's cost of debt:

A) could be caused by an increase in the firm's tax rate.
B) will result in an increase in the firm's cost of capital.
C) will lower the firm's weighted average cost of capital.
D) will lower the firm's cost of equity.
E) will increase the firm's capital structure weight of debt.