Which of the following statements regarding provisions for paying off bonds is least likely correct（）

A. Nonrefundable bonds can be callable.

B. Serial bonds are an issue with several staggered maturity dates.

C. A sinking fund provision gives the company the option to retire portions of the bond issue prior to maturity.

二十四桥仍在，______，______。念桥边红药，年年知为谁生!(姜夔《扬州慢》)