Explanation/Reference:
B (not A): Oracle Exadata components-including database and storage servers, switches, and power distribution units (PDUs)-use SNMP to raise alerts and report monitoring information.
Oracle's CellCLI interface is a Java-based framework delivered by the storage cell's management server process (MS) that provides administrative capabilities to your storage server entities.
C: Cloud control can monitor the Exadata Database Machine.
Figure: Oracle Enterprise Manager Cloud Control 12c monitoring architecture. Note the Management Server process (MS) on the Storage servers.

G (not D): Before using Oracle Enterprise Manager Cloud Control 12c with Oracle Exadata, an Oracle Management Agent and Oracle Exadata plug-in must be installed on every Oracle Exadata database server (compute node). This agent monitors software targets, such as the database instances and Oracle Clusterware resources, on the database servers. The plug-in enables monitoring of other hardware components in Oracle Exadata, including the storage servers, switches, and power distribution units.
References: http://www.oracle.com/technetwork/articles/servers-storage-admin/monitor-exadata-em12-
2291964.html