Which statement correctly describes setup of a server-persistent parameter file (SPFILE) when used with Real Application Clusters?

Which statement correctly describes setup of a server-persistent parameter file (SPFILE) when used with Real Application Clusters?

A.
One SPFILE, created from a text parameter file (PFILE), is required for each instance

B.
You must create a separate text parameter file (PFILE) for each instance and merge them with CREATE SPFILE FROM PFILE= (list of files ); command to create one common SPFILE

C.
You can add the instance-specific parameters to a common SPFILE with the ALTER SYSTEM ? SCOPE = SPFILE SID = name ; command.

D.
One common SPFILE is required for all instances; it has a parameter INSTANCE_name_SPFILE, which in turn points to the instance-specific SPFILE

Explanation:
All instances in the cluster database use the same SPFILE at startup. Oracle recommends, you to use one shared server parameter file (SPFILE) with instance-specific entries. For example, you assign undo tablespaces in your RAC database by specifying a different value for the UNDO_TABLESPACE parameter for each instance in your SPFILE or individual PFILEs.

REF: Oracle(r) 10g Database Oracle Clusterware and Oracle Real Application Clusters Guide, 5-7