What is necessary for a subject to have read access to an object in a Multi-Level Security Policy?什么对于主体在多层安全策略中拥有对一个客体的访问权限是必要的？（）

• A、The subject's sensitivity label must dominate the object's sensitivity label.主体的敏感性标识必须支配客体的敏感性标识
• B、The subject's sensitivity label subordinates the object's sensitivity label.主体的敏感性标识从属于客体的敏感性标识
• C、The subject's sensitivity label is subordinated by the object's sensitivity label.主体的敏感性标识被客体的敏感性标识从属
• D、The subject's sensitivity label is dominated by the object's sensitivity label.主体的敏感性标识以客体的敏感性标识为主体