Often central governments will announce auctions to issue new bonds when they believe prevailing market conditions appear most suitable. At the time of the auction, the amount to be auctioned and the maturity of the security to be offered are announced. This method of distributing new government securities is called:（）
A. an ad hoc auction method.
B. a regular auction cycle/multiple-price method.
C. a regular auction cycle/single-price method.
