When a Bond Payable Is Issued at a Premium,subsequent Amortization

When a bond payable is issued at a premium,subsequent amortization of the premium does which of the following?

A) Increase interest expense.
B) Decrease the book value of the bonds.
C) Decrease in amount amortized for each year the bond gets older when the effective-interest method is used.
D) Decrease the amount reported as a cash flow from operating activities.