What are some necessary parts of the singleton pattern?

Comprehensive and Detailed Explanation From Exact Extract:

Modern ABAP encourages well-structured OO patterns under ABAP for Cloud Development, with static checks and typed APIs. A singleton is realized by:

Preventing external instantiation (CREATE PRIVATE).

Holding a static reference attribute to the single instance.

Providing a public static factory (get_instance) that returns the single instance.This aligns with the ABAP Cloud guidance on architecture-driven, upgrade-stable design (strict language, typed APIs, static checks).

(C) is wrong: the factory method must be public so callers can get the instance.