Mass is a property of a lump of matter. It goes wherever the lump goes,
and it doesn't depend on what else may be nearby.
Weight is the force of gravity between a lump of matter and some other
mass. Since it depends on what else may be nearby, it can be different in
different places.
This is the correct answer in Physical Science. It's also the correct answer
in Biology, Math, Political Science, and Comparative Middle Eastern Religions.
