List three human activities which would lead to an increase in the carbon dioxide content of air.
Human activities which would lead to an increase in the carbon dioxide content of air are as follows:
(i) Burning of fuels in various processes like heating, cooking, transportation, and industry.
(ii) Human induced forest fires
(iii) The process of deforestation includes the cutting down of trees. This decreases the uptake of carbon dioxide for photosynthesis. Eventually, the content of carbon dioxide increases.