The correct option is A Acid rain
Acid rain is precipitation that has the pH which is less than that of the pH of natural rainwater. This is the reason behind the stiffness of flower buds. The pHdetermines whether the solution is acidic or basic. The process of combustion produces carbon monoxide, nitrogen oxide. These gases contribute to air pollution. When sulphur dioxide and the nitrogen oxides present in the atmosphere mix with water vapours, it forms Sulphuric acid or nitric acid or it leads to acid rain. Taj Mahal is being slowly disfigured and discolored due to the reaction of calcium carbonate i.e. marble with the Sulphuric acid and nitric acid present in the rain and form calcium sulphate which is more soluble than calcium carbonate. This results in the erosion of the beautiful monument. The reaction involved is:
CaCO3+H2SO4→CaSO4+CO2+H2O
Hence the correct answer is (D) acid rain.