确定打开可插拔数据库(PDBs)的三种有效方法是？ ACG A、从当前PDB执行ALTER DATABASE OPEN B、从种子PDB执行ALTER PLUGGABLE DATABASE PDB OPEN C、从根执行ALTER PLUGGABLE DATABASE OPEN ALL D、从另一个PDB执行ALTER PLUGGABLE DATABASE PDB OPEN E、从一个PDB中执行ALTER PLUGGABLE DATABASE OPEN ALL F、从根执行ALTER DATABASE PDB OPEN G、从当前PDB执行ALTER PLUGGABLE DATABASE OPEN