When we say that the weight of an object is Mg, and that g = 9.8 N/kg, what assumptions are we making?

Question

Which of the below?

The distribution of mass in the earth is spherically symmetric.
The density of the earth is the same everywhere.
The earth's interior is solid everywhere.
The orbit of the earth is circular and not elliptical.
We neglect the effect of astronomical bodies other than the earth.
The object is at the earth's surface.
Two significant figures are sufficient.
Newton's law of gravitation holds.