单项选择题:
Bonds issued by a country's central government are referred to as sovereign bonds. Which of the following ruethods is used by central governments to issue sovereign bonds when it determines market conditions are advantageous（）
A. Regular cycle auction (multiple price). B. An ad hoc auction system. C. A tap system.
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答案：B
解析: 在市场适合的隋况下，选择发行债券属于特别的拍卖系统。