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.