Which of the following has been causing most damage to the Taj Mahal?

Acid rain

Taj Mahal is situated in Agra which has a number of industries. The pollutants from industries are released in the air which include oxides of sulphur and nitrogen.

The oxides of sulphur and nitrogen react with water vapours in the atmosphere and form sulphuric acid and nitric acid which come down on earth in the form of rain and this is known as acid rain.

The acid rain reacts with the marble of Taj Mahal which is made up of calcium carbonate and this has resulted in the change of colour of marble of Taj Mahal from white to pale yellow.

Thus acid rain due to industrialization in Agra is damaging the Taj Mahal.