Which of these is most directly related to the mass of an object?

Weight

Acceleration

Volume

Inertia

Weight is the force with which gravity pulls on a mass. so most directly related to the mass of an object is weight

Weight is directly related to mass, but it also

depends on the local gravity.

Acceleration is directly related to mass, but it also

depends on the net force acting on the mass.

Volume is directly related to mass, but it also

depends on the density of the object or sample.

Inertia is directly related to mass, and is completely determined

by the mass. It doesn't depend on anything else, so this may be

the best choice.