A simple PL/SQL Block

A simple PL/SQL Block:
1) SQL>BEGIN
                       NULL;
              END;
->NULL Block.

2) SQL>BEGIN
                      RETURN;
               END;

->BLOCK with RETURN clause.

3) SQL>DECLARE
              BEGIN
                      NULL;
              END;

 
4) SQL>DECLARE
              BEGIN
                       NULL;
              EXCEPTION
                       WITH OTHERS THEN
              NULL;
              END;