Which of the following is least likely allowed if a bond is non-refundable A corporation:（）

A. issues zero coupon bonds at a yield that is lower than the current rate on their bonds and redeems the old bond issue.

B. calls its nonrefundable bonds and issues common equity in their place.

C. gets a revolving credit line at the bank at a rate lower than that on their bonds and redeems the bonds.

病毒自启动方式一般有（）

A、修改注册表

B、将自身添加为服务

C、将自身添加到启动文件夹

D、修改系统配置文件