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: 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 manipulatio