A. Interface elements are always provided as proprietary packages of widgets from device vendors and third parties.

B. There is a wide variety of interface elements that can be developed once and used repeatedly in various user-interface designs.

C. Interface elements are highly standardized and, once developed for one device, they are sufficiently portable to be reused on other devices without modification.

D. Interface elements implement application-specific functionality and are therefore rarely reusable across multiple applications.