Module-based programming language is —

Programming languages are commonly grouped by their organizing paradigm — procedural, object-oriented, functional, logic, and module-based. A module-based language builds programs around the module/package as the core unit: a construct that separates a public interface (specification) from a private implementation (body), enforces encapsulation, and supports separate compilation of units.

Among the given options, Ada is built around exactly this construct — the package. An Ada package splits into a public specification and a private body, hides implementation details behind that interface, and can be compiled separately from the units that use it. This package-centric design is why Ada is the standard textbook example cited for the module-based category.

• C has no package/module keyword at all — modularity is only a convention of splitting code into header (.h) and source (.c) files, tied together by the linker, not a language-level construct.

• Classical C++ (pre-C++20) still relies on the same header/source-file convention as C; in this paradigm taxonomy C++ is placed under the object-oriented category, not module-based.

• ML has a genuine module system — structures, signatures, and functors — but the paradigm taxonomy classifies ML under functional languages, not module-based.

So, of the four options, only Ada is classified as the module-based programming language.