Pedagogy is a:

Pedagogy is the academic discipline that studies the theory and practice of teaching — it covers instructional methods, curriculum design, classroom strategies, and how educational content is delivered to learners; in short, it is the study of how teaching itself is carried out.

The stem asks for pedagogy's core identity. Because pedagogy centers on the practice and theory of instruction — not on learners' internal cognitive processes alone, not on behavior in general, and not on assessment techniques alone — the option that names it as the discipline of teaching is the one that matches this definition.

• Science of behavior names behaviorism, the psychological study of stimulus-response conditioning in organisms generally — a distinct branch of psychology, not the meaning pedagogy carries.

• Science of learning names cognitive/learning science — how learners acquire, retain, and process information — a related but separate concern from how teaching is conducted.

• Science of testing names psychometrics/assessment science — measuring ability or performance — one narrow evaluative tool within teaching, not the whole discipline.

So pedagogy is correctly defined as the science of teaching — the field devoted to how teaching is planned, delivered, and refined, which is exactly why competitive teaching exams such as this one test it as a foundational term.