Question

the burning of fossil fuels releases which of the following gases into the atmosphere?
oxygen
carbon dioxide
nitrate
nitrogen

Explanation:

Fossil fuels are composed of carbon and hydrogen. When burned, they react with oxygen. The main product is carbon dioxide ($CO_2$). Oxygen is consumed in the burning process, nitrate is not a gas released in this context, and nitrogen is not a product of fossil - fuel combustion in significant amounts as a direct result of the burning reaction.

Answer:

carbon dioxide