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 anda"system high"evaluation.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。