Which has more mass: an armful of feathers or an armful of lead? which has more volume: a kilogram of feathers or a kilogram of lead? which has higher density: a kilogram of feathers or a kilogram of lead?

Mass is related to weight. It measures the resistance of the substance to acceleration when a net force is applied.
Therefore: armful of lead has more mass

volume measures the amount of 3-dimensional space that an object occupies.
Therefore: kilogram of feather has more volume as it is less dense.

density is the mass per unit volume. Since armful of lead has more mass than a handful of feathers, while kilogram of feather has more volume than a kilogram of lead.
Therefore: kilogram of lead has higher density.

D. most models represent a real world object in a simpler way

  super sorry but i dont know lo