The primary way carbon is transferred from plants and animals to the soil is through the decay of dead organisms and the decomposition of organic matter. During this process, microorganisms break down the carbon-containing compounds in dead plants and animals, releasing carbon in various forms, including carbon dioxide (CO2) and organic materials that contribute to soil organic matter.
Out of the options you've provided, the most accurate statement is:
The decay of dead organisms releases some carbon atoms from their bodies into the soil.
This encompasses the breakdown of organic matter and the subsequent transfer of carbon to the soil. While carbon dioxide is released during respiration and decomposition, the phrase "some carbon atoms" reflects the broader process of carbon cycling, including the various forms of carbon that contribute to soil health and fertility.