Concept:Scalar quantities have only magnitude (size) and no direction. Vector quantities have both magnitude and direction.Explanation:Mass is a scalar because it measures only the amount of matter in an object; it has no direction.Acceleration due to gravity is a vector; it points downward toward Earth's center.Momentum is a vector; it depends on velocity, which has direction.Weight is a vector; it is the force of gravity acting downward.Thus, among the given options, only mass is a scalar quantity.Answer:Option A: Mass