Unfortunately, I am not sure that some of the answers given here are correct! The confusion may be arising with the wording of the question If you look at the answer choices they are all expressed in terms of a percent of the mass of the object, not a percent of the weight of the object.
A distinction has to be made between the mass of the object, given by m, and its weight, which is mg. The weight of an object can be different under different conditions because this depends on g, however, the mass will remain the same unless it is being converted to energy (E = mc^2).
Therefore, in terms of the mass, I think the correct answer is A, i.e. 100% of its mass! Regardless of the upward forces experienced by an object, it will always press down on something below it with 100% of its mass.