Which of the above are valid definitions for associative arrays?

Associative arrays let you insert elements using arbitrary key values. The keys need not be consecutive.

The key data type can be PLS_INTEGER, VARCHAR2, or one of VARCHAR2 subtypes VARCHAR, STRING, or LONG.

You must specify the length of a VARCHAR2-based key, except for LONG which is equivalent to declaring a key type of VARCHAR2(32760). The types RAW, LONG RAW, ROWID, CHAR, and CHARACTER are not allowed as keys for an associative array. The LONG and LONG RAW data types are supported only for backward compatibility; see LONG and LONG RAW Data Types for more information.

An initialization clause is not allowed. There is no constructor notation for associative arrays. When you reference an element of an associative array that uses a VARCHAR2-based key, you can use other types, such as DATE or TIMESTAMP, as long as they can be converted to VARCHAR2 with the TO_CHAR function.

CREATE TABLE HR.DEPARTMENTS
(
DEPARTMENT_ID NUMBER(4),
DEPARTMENT_NAME VARCHAR2(30 BYTE) CONSTRAINT DEPT_NAME_NN NOT NULL,
MANAGER_ID NUMBER(6),
LOCATION_ID NUMBER(4),
MAIN_PHONE VARCHAR2(20 BYTE),
TITLE VARCHAR2(80 BYTE)
)

TYPE tb1 IS TABLE OF departments.department_name%TYPE INDEX BY NUMBER;
TYPE tb2 IS TABLE OF va1 INDEX BY PLS_INTEGER;
TYPE tb3 IS TABLE OF scale INDEX BY VARCHAR2(10);
TYPE tb4 IS TABLE OF DATE INDEX BY DATE;
TYPE tb5 IS TABLE OF NUMBER INDEX BY CHAR(2);

ALL associative array … index by
not RAW, LONG RAW, ROWID, CHAR, and CHARACTER and
let you insert elements using arbitrary key values.

PIERO!
Such a stupid moron…
Think then write, don’t write then think.