Which of the following is not a type of internal table in ABAP?

In ABAP, internal tables are data structures used to hold multiple rows of data, similar to an array or a list. There are three primary types of internal tables that are widely recognized: standard tables, sorted tables, and hashed tables.

A standard table is the default type of internal table. It allows for simple addition and deletion of entries and can be accessed using index-based methods. A sorted table maintains its entries in a sorted order based on the specified sort criteria, which allows for efficient sorting but may incur additional overhead upon insertion. A hashed table uses a unique key to provide very fast access to its entries, as it employs a hashing algorithm for quick lookups.

The term "virtual table" is not recognized as an official type of internal table in ABAP. While it may suggest a structure that provides a view of data, it does not conform to the definitions of standard, sorted, or hashed tables utilized within the ABAP programming environment. Therefore, recognizing that the other types of internal tables are defined and employed in ABAP makes it clear why "virtual table" is not a valid type.