A (not B, not E): The CREATE DATABASE ... ENABLE PLUGGABLE DATABASE SQL statement creates a new CDB. If you do not specify the ENABLE PLUGGABLE DATABASE clause, then the newly created database is a non-CDB and can never contain PDBs.
D: You can create a PDB by plugging in a Non-CDB as a PDB.
The following graphic depicts the options for creating a PDB:

Incorrect Answers:
E: For the duration of its existence, a database is either a CDB or a non-CDB. You cannot transform a non- CDB into a CDB or vice versa. You must define a database as a CDB at creation, and then create PDBs within this CDB.

Note:
* Oracle 12c now provides the ability to index a subset of partitions and to exclude the others.
Local and global indexes can now be created on a subset of the partitions of a table. Partial Global indexes provide more flexibility in index creation for partitioned tables. For example, index segments can be omitted for the most recent partitions to ensure maximum data ingest rates without impacting the overall data model and access for the partitioned object.
Partial Global Indexes save space and improve performance during loads and queries. This feature supports global indexes that include or index a certain subset of table partitions or subpartitions, and exclude the others. This operation is supported using a default table indexing property. When a table is created or altered, a default indexing property can be specified for the table or its partitions.

A: The APPEND keyword tells SQL*Loader to preserve any preexisting data in the table. Other options allow you to delete preexisting data, or to fail with an error if the table is not empty to begin with.
B (not D): Note:
* SQL*Loader-00210: first data file is empty, cannot process the FIELD NAMES record Cause: The data file listed in the next message was empty. Therefore, the FIELD NAMES FIRST FILE directive could not be processed. Action: Check the listed data file and fix it. Then retry the operation
E:
*A comma-separated values (CSV) (also sometimes called character-separated values, because
the separator character does not have to be a comma) file stores tabular data (numbers and text)
in plain-text form. Plain text means that the file is a sequence of characters, with no data that has
to be interpreted instead, as binary numbers. A CSV file consists of any number of records,
separated by line breaks of some kind; each record consists of fields, separated by some other
character or string, most commonly a literal comma or tab. Usually, all records have an identical
sequence of fields.
*Fields with embedded commas must be quoted.
Example:
1997,Ford,E350,"Super, luxurious truck"
Note:
*SQL*Loader is a bulk loader utility used for moving data from external files into the Oracle database.

Explanation/Reference:
Explanation:
B: SYSDG administrative privilege has ability to perform Data Guard operations (including startup and shutdown) using Data Guard Broker or dgmgrl.
D: SYSASM
The new (introduced in 11g) SYSASM role to manage the ASM instance, variable extent sizes to reduce shared pool usage, and the ability of an instance to read from a specific disk of a diskgroup E (Not A): SYSDBA is like a role in the sense that it is granted, but SYSDBA is a special built-in privilege to allow the DBA full control over the database
Incorrect Answers:
C: SYSKM. SYSKM administrative privilege has ability to perform transparent data encryption wallet operations.
Note:
Use the V$PWFILE_USERS view to see the users who have been granted administrative privileges.