问题：

[单选题]debt security pays ()xCB答案窝(daanwo.com)-大学作业答案分享平台
Aa fixed level of income for the life of the owner.xCB答案窝(daanwo.com)-大学作业答案分享平台
Ba variable level of income for owners on a fixed income.xCB答案窝(daanwo.com)-大学作业答案分享平台
Ca fixed or variable income stream at the option of the owner.xCB答案窝(daanwo.com)-大学作业答案分享平台
Da fixed stream of income or a stream of income that is determined according to a specified formula for the life of the security.