You administer a RAC database that currently runs on a four-node cluster but which has...

A thread of redo must be created before starting a fourth instance if a thread is not already available.

A thread of redo is automatically dropped when an instance is removed from a RAC database by usingSRVCTL.

All the instances must have the same number of redo log groups and each group must have the same number of redo log members.

A redo log group added using alter database add logfile without the instance clause is added to each instance.

A thread of redo must contain at least two log groups before it can be enabled.