Which is primarily taught and researched at the university level, involving…

An "academic discipline" is a specialized branch of knowledge organized around its own theories, concepts, and research methods, and advanced mainly by a community of scholars who conduct systematic research — chiefly at universities — to produce new knowledge. This differs from a "school subject" (the discipline's content re-packaged and simplified for classroom teaching), a "practical skill" (an applied competence built through training and practice), and a "curriculum" (the overall plan of what is taught, not a body of knowledge itself).

The stem names two defining features together: the field is primarily taught AND researched at the university level, and it involves the systematic production of new knowledge by experts. A skill is built through practice rather than research; a school subject is taught mainly at school, not primarily researched at university; and a curriculum is a plan of study, not a body of created knowledge. Only "An academic discipline" satisfies both features together, so it is the correct answer.

• A practical skill — an applied competence developed through training and repeated practice (e.g., a craft or trade), not through university-based research.

• A school subject — the curriculum-packaged, simplified version of a field of knowledge taught to school students; it is taught, not researched, at that level.

• A general curriculum — the overall course of study or framework an institution offers; it organizes what is taught, it does not itself constitute researched knowledge.