Burning of fossil fuels: fossil fuels like coal, oil and natural gas have become an integral part of our life. they are used on large basis to produce electricity and for transportation. when they are burnt, the carbon stored inside them is released which combines with oxygen in the air to create carbon dioxide. with the increase in the population, the number of vehicles have also increased and this has resulted in increase in the pollution in the atmosphere. when these vehicles run, they release carbon dioxide, which is one the main gas responsible for increase in greenhouse effect.

what is a cause in the paragraph above?

a. " carbon stored inside them is released which combines with oxygen in the air to create carbon dioxide."

b. "when they are burnt, "