The Taj Mahal is suffering from "Marble Cancer" due to the presence of sulphur dioxide. Sulphur dioxide is a pollutant that is released into the air by burning fossil fuels, industrial emissions, and other human activities. When sulphur dioxide combines with moisture in the air, it forms a weak acid called sulphuric acid. This acid then reacts with the marble surface of the Taj Mahal, causing it to deteriorate over time.

Option 2 (nitrogen dioxide) is not the correct answer because nitrogen dioxide does not directly contribute to the degradation of the Taj Mahal. However, it does contribute to air pollution and can have negative effects on human health.

Option 3 (chlorofluorocarbon) is also incorrect as chlorofluorocarbons are not involved in the deterioration of marble. Chlorofluorocarbons are synthetic chemicals that were previously used in aerosol sprays and refrigeration systems, but they are known for depleting the ozone layer.

Option 4 (carbon dioxide) is not the main culprit for the "Marble Cancer" as it does not directly react with the marble to cause deterioration. However, carbon dioxide does contribute to climate change and acidification of the oceans.