In a class you use the statement DATA var TYPE …What may stand in place...

Comprehensive and Detailed Explanation from Exact Extract:

The ABAP DATA statement declares a variable with an assigned type.

A. Private type in the same class (ZCL_CLASS_A) → ✅ Allowed. A class can use its own local type definitions, declared using TYPES.

B. Domain from ABAP Dictionary → ❌ Not allowed directly. Domains define technical attributes but cannot be referenced directly in DATA; they must be wrapped in a data element.

C. Type defined privately in another class → ❌ Not accessible, since private definitions are encapsulated.

D. Data element from ABAP Dictionary → ✅ Allowed, because data elements are global dictionary objects.

This follows ABAP Cloud extensibility rules, ensuring encapsulation and strict typing.

Verified Study Guide Reference: ABAP Dictionary Development Guide, ABAP Cloud Back-End Developer Learning Material (Variable Typing and Encapsulation).