Which of the following are necessary components of a Multi-Level Security Policy? 下面哪项是多级安全策略的必要组成部分吗？（）

A、Sensitivity Labels for only objects and Mandatory Access Control.适合于唯一客体的敏感标记和强制访问控制。

B、Sensitivity Labels for subjects&objects andasystem highevaluation.适合于主体与客体的敏感标记以及“高级别系统”评价。

C、Security Clearances for subjects&Security Labels for objects and Mandatory Access Control.主体安全声明&适合于唯一客体的敏感标记和强制访问控制。

D、Sensitivity Labels for subjects&objects and Discretionary Access Control.适合于主体与客体的敏感标记和自主访问控制。