Explanation/Reference:
C, F: All backup operations can be offloaded to a single standby database, except backups of the SPFILE.
Backups of the SPFILE can only be restored to the database from which they were backed up.
E: RMAN restores database files, over the network, from a physical standby database.
As of Oracle Database 12c, RMAN lets you restore or recover files by connecting, over the network, to a physical standby database that contains the required files. You can restore an entire database, data files, control files, spfile, or tablespaces.
Note: An Oracle database consists of one or more logical storage units called tablespaces, which collectively store all of the database's data. Each tablespace in an Oracle database consists of one or more files called datafiles, which are physical structures that conform to the operating system in which Oracle is running.
References: https://docs.oracle.com/database/121/SBYDB/rman.htm#SBYDB00755