在oracle数据库中，想要修改AWR快照的间隔为30分钟，下面的哪个命令可以实现？ A exec dbms_workload_repository.modify_snapshot_settings(interval => 0.5); B exec dbms_workload_repository.modify_snapshot_settings(interval => 0); C exec dbms_workload_repository.modify_snapshot_settings(interval => 60); D exec dbms_workload_repository.modify_snapshot_settings(interval => 30);