(A) When 600cm3 of air is pumped into Flask A, the balance will tip in favor of Flask A. This is because the additional 600cm3 of air has added to the overall mass of air in Flask A.
(B) The volume of air in Flask A is unchanged at 1000cm3. This is because the Flask is made of solid glass that cannot expand easily even as the pressure of air in the flask increases.
(C) The experiment demonstrates that air (i) has mass and (ii) can be compressed.