Which of the above are valid definitions for associative arrays?

Examine the code snippet from the declarative section of a PL/SQL block:
DECLARE
TYPE va1 IS VARRAY(10) OF VARCHAR2(20);
SUBTYPE scale IS NUMBER(1,0);
TYPE tb1 IS TABLE OF departments.department_name%TYPE INDEX BY
departments.department_id%TYPE;
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);
….
Which of the above are valid definitions for associative arrays? (Choose all that apply.)

A.
tb1

B.
tb2

C.
tb3

D.
tb4

E.
tb5