Which three statements are true concerning the use of the Valid Time Temporal feature for the EMPLOYEES table?

You create a table with the period for clause to enable the use of the Temporal Validity
feature of Oracle Database 12c.
Examine the table definition:
create table employees
(empno number, salary number,
deptid number, name varchar2(100),
period for employee_time);
Which three statements are true concerning the use of the Valid Time Temporal feature for
the EMPLOYEES table?

A.
The valid time columns employee_time_start and employee_time_end are automatically
created.

B.
The same statement may filter on both transaction time and valid temporal time by using
the AS OF TIMESTAMP and PERIOD FOR clauses.

C.
The valid time columns are not populated by the Oracle Server automatically.

D.
The valid time columns are visible by default when the table is described.

E.
Setting the session valid time using
DBMS_FLASHBACK_ARCHIVE.ENABLE_AT_VALID_TIME sets the visibility for data
manipulation language (DML), data definition language (DDL), and queries performed by the
session.

Explanation:
A: To implement Temporal Validity(TV), 12c offers the option to have two date columns in
that table which is having TV enabled using the new clause Period For in the Create Table
for the newly created tables or in the Alter Table for the existing ones. The columns that are
used can be defined while creating the table itself and will be used in the Period For clause
or you can skip having them in the table’s definition in the case of which, the Period For
clause would be creating them internally.
E: ENABLE_AT_VALID_TIME Procedure
This procedure enables session level valid time flashback.