List any three human activities which could lead to an increase in carbon dioxide content of air.

•Burning of fossil fuels like coal and petroleum releases carbon dioxide in the atmosphere.

•Deforestation also causes increase in carbon dioxide content as the plants that use carbon dioxide are cut down.

•Industries release various harmful gases into the atmosphere. Carbon dioxide is one such gas.

•Overpopulation will also lead to increase in carbon dioxide content as humans release carbon dioxide by respiration.