How to open pluggable database (PDBs) in Oracle 19 C

C:\WINDOWS\system32>sqlplus /nolog
SQL*Plus: Release 19.0.0.0.0 - Production on Wed Mar 25 21:53:59 2020
Version 19.3.0.0.0
Copyright (c) 1982, 2019, Oracle.  All rights reserved.
SQL> conn sys/orcl as sysdba
Connected.
SQL> show pdbs
    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 ONTOOR                         READ WRITE NO
         4 APEX_5                         MOUNTED
         5 APEX_19_2                      READ WRITE NO
         6 APEX_18_2                      READ WRITE NO
SQL>


SQL> alter pluggable database APEX_5 open;
Pluggable database altered.
SQL> show pdbs
    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 ONTOOR                         READ WRITE NO
         4 APEX_5                         READ WRITE NO
         5 APEX_19_2                      READ WRITE NO
         6 APEX_18_2                      READ WRITE NO
SQL>


CREATE OR REPLACE TRIGGER open_all_pdbs
   AFTER STARTUP
   ON DATABASE
BEGIN
   EXECUTE IMMEDIATE 'alter pluggable database all open';
END open_all_pdbs;

ALTER PLUGGABLE DATABASE apex_5 CLOSE;

ALTER SESSION SET CONTAINER = apex_5;