If a company's bonds are callable:

a. the bondholder has the right to sell an option on the bond.

b. the bonds are never allowed to remain outstanding until the maturity date.

c. the investor never knows what the redemption price will be until the bonds are actually called.

d. the issuing company is likely to retire the bonds before maturity if the bonds are paying 8% interest while the market rate of interest is 4%.