Inertia is the tendency of an object to resist a change in . Newton’s first law of states that an object at rest will stay at rest unless it is acted upon by an outside force.

Inertia is an object's tendency to resist changes in its motion, so “motion” fits the first blank. Newton’s first law of motion describes how an object remains at rest or continues moving unless an outside force acts on it. Therefore, the correct choice is B, motion.

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