The Pre-Tax Cost of Debt for a Firm

The pre-tax cost of debt for a firm:

A) is equal to the yield to maturity on the outstanding bonds of the firm.
B) is equal to the coupon rate of the outstanding bonds of the firm.
C) is equivalent to the current yield on the outstanding bonds of the firm.
D) is based on the yield to maturity that existed when the currently outstanding bonds were originally issued.
E) has to be estimated as it cannot be directly observed in the market.