Which of the Earth's subsystems is directly affected by burning fossil fuels?

geosphere

hydrosphere

biosphere

atmosphere

The correct answer is option (d) atmosphere.

Fossil fuels are the hydrocarbons formed in the geological past, derived from the remains of dead plants and animals. They include the coal, fuel gas and the natural gas. The burning of fossil fuels is one of the greatest contributor of carbon dioxide being added to the atmosphere. This results in the pollution of air in the atmosphere resulting in the formation of smog. Carbon dioxide being a green house gas, affects the atmosphere and causes green house effect leading to global warming and climate changes.

The burning of fossil fuels affects the geosphere, biosphere and hydrosphere indirectly due to its primary direct effect on the atmosphere. Thus, atmosphere is directly affected by the burning of fossil fuels.

Burning fossil fuels puts pollution into the air, meaning you're affecting the atmosphere.