Q:3 List any three human activities which would lead to an increase in the carbon dioxide content of air.
Three human activities which would lead to an increase in the carbon dioxide content of air are:
(i) Combustion of fossil fuels like coal and petroleum releases carbon dioxide in the atmosphere.
(ii) Deforestation leads to an increase in carbon dioxide content in the atmosphere.
(iii) The smoke released from industries contains many harmful gases including carbon dioxide into the atmosphere.