Given a scenario or question, the learner identifies whether the question asks about U3.A6 (mass as inertial obstacle to motion change) or A13 / R1 (mass as source of gravitational pull) — a non-comparative type-discrimination — and applies the correct rule for the answer. Critically, the learner correctly answers that an orbiter's own mass does NOT determine its orbit size (D6: M1 anti-target).