Which of the Following Statements Is Most Correct

Which of the following statements is most correct?

A) If a company's tax rate increases but the yield to maturity of its non-callable bonds remains the same, the company's marginal cost of debt capital used to calculate its weighted average cost of capital will fall.
B) All else equal, an increase in a company's shares price will increase the marginal cost of retained earnings.
C) All else equal, an increase in a company's share price will increase the marginal cost of issuing new ordinary equity.
D) Answers a and b are both correct.
E) Answers b and c are both correct.