The Taj Mahal, one of the seven wonders of the world is losing its charm due to which of the given reason?

The Taj Mahal, one of the seven wonders of the world is losing its charm due to acid rain caused by air pollutants.
Taj Mahal is made of marble which is mainly composed of calcium carbonate (CaCO₃), this CaCO₃ reacts with acid precipitated due to air pollutants (SO_2, due to vehicle exhaust).
CaCO₃ (Marble of Taj Mahal) + SO₂ (Vehicle exhaust) + H₂O (Rain) -------> CaSO₄ (pale yellow substance, Calcium sulphate)