Which two statements are true about associative arrays and nested tables? (Choose two.)
A.
Only associative arrays can hold an arbitrary number of elements.
B.
Only associative arrays can use numbers and strings for subscripts.
C.
Both associative arrays and nested tables can hold an arbitrary number of elements.
D.
Both associative arrays and nested tables can use numbers and strings for subscripts.
B, C.
http://docs.oracle.com/cd/B19306_01/appdev.102/b14261/collections.htm
Associative arrays, also known as index-by tables, let you look up elements using *arbitrary numbers and strings for subscript values*. These are similar to hash tables in other programming languages.
Nested tables hold an arbitrary number of elements. They use sequential numbers as subscripts. You can define equivalent SQL types, allowing nested tables to be stored in database tables and manipulated through SQL.
A , B
B ,C