In object$-$oriented development:

A$)$ data categories are described as distinct objects, which can share characteristics with other objects.

B$)$ data is separated into discrete, reusable objects that any processes may act upon.

C$)$ an object comprises a single, reusable program that can be combined with other objects to form a robust application.

D$)$ an object combines data and processes that act on the data into a single object.