How are version related upgrades passed on to subscriber API extensions/overrides?

How are version related upgrades passed on to subscriber API extensions/overrides?
A . APIs callback with specific versions specified; the user must know which version number to use.
B . Copy and paste of specific code is "built-in"
C . Extensions and overridden APIs don’t support-related upgrades.
D . The "delegate" allows inherited method calls access to the most recentlyspecified service version

Answer: D

Explanation:

Version related upgrades are passed on to subscriber API extensions/overrides by using the “delegate” keyword, which allows inherited method calls access to the most recently specified service version. For example, delegate.getCart() will invoke the getCart() method of the latest service version that is available for the current storefront. This way, extensions and overrides can leverage the new features and enhancements of the upgraded service versions without modifying their code.