Which One of the Following Statements Is Accurate for a Levered

Which one of the following statements is accurate for a levered firm?

A) A firm's WACC will decrease whenever the firm's tax rate decreases.
B) The subjective approach totally ignores a firm's own WACC.
C) WACC should be used as the required return for all proposed investments.
D) An increase in the market risk premium will decrease a firm's WACC.
E) A reduction in the risk level of a firm will tend to decrease the firm's WACC.