In Recovery Manager （RMAN）， you set the retention policy to NONE by executing the following command：  CONFIGURE RETENTION POLICY TO NONE;  What would be the impact of this setting？（）

• A、The retention policy is cleared.
• B、RMAN does not consider any backup as obsolete.
• C、The retention policy is set to its default setting of redundancy 1.
• D、The retention policy is set to its default setting of recovery window 7.