Question

........................ gas causes green house effect that mostly increases due to use of fossil fuels

Answer 1

Burning or combustion of fossil fuels releases carbon dioxide which is a greenhouse gas. It absorbs the radiation of sun and prevents it from getting escaped after reflecting from earth's surface. This results in increase in temperature of earth's surface which is called greenhouse effect. Excess rise in temperature of earth leads to global warming in which temperature of earth rises abnormally due to excess concentration of carbon dioxide.

So, the correct answer is 'carbon dioxide'.