Question

what is the primary impact of combustion of fossil fuels on the carbon cycle? it releases vast amounts of co2 into the atmosphere it decreases atmospheric co2 it converts co2 into sugars it dissolves co2 into seawater

Explanation:

Fossil fuels contain carbon. When burned (combusted), they react with oxygen. The chemical reaction releases carbon dioxide ($CO_2$) as a by - product. This $CO_2$ enters the atmosphere. Photosynthesis (which converts $CO_2$ into sugars) is a process of plants, not related to fossil fuel combustion. Dissolving $CO_2$ into seawater is a natural carbon - sequestering process but not the direct impact of fossil fuel combustion. And fossil fuel combustion increases, not decreases, atmospheric $CO_2$.

Answer:

It releases vast amounts of $CO2$ into the atmosphere.