External tables using the ORACLE_DATAPUMP access driver have specific characteristics:
C . Creating an external table using the ORACLE_DATAPUMP access driver allows you to select data from other tables, including another external table or a regular table whose rows are stored in database blocks.
A, B, D, and E are incorrect. Specifically:
A is incorrect because creating an external table does not automatically create a directory object; the directory object must exist prior to or be created separately.
B is incorrect as it limits the creation to tables stored in database blocks, which is not a restriction.
D is incorrect because creating an external table does not create a dump file; it reads from an existing dump file created by Data Pump.
E is also incorrect because the dump file is not created as part of the external table creation process.
Reference:
Oracle Database SQL Language Reference, 12c Release 1 (12.1): "CREATE TABLE" for External Tables