Which of the Following Statements Is True

Which of the following statements is true?

A) Using the same WACC to discount all a firm's potential investments is a sound financial practice.
B) When a firm has debt in its capital structure,the cost of equity is the appropriate discount rate to use in NPV calculations.
C) If an investment being evaluated has higher risk than the firm's current set of projects,the firm's WACC is the appropriate discount rate to use.
D) Statements (a) and (b) are true
E) All of the above statements are false.