Which of the following processes is expected to reduce atmospheric carbon levels?

The process of decaying plant and animal remains and the formation of carbonate rock in the ocean plays a significant role in reducing atmospheric carbon levels. This occurs through a natural carbon sequestration process, where organic matter, as it decomposes, can lead to the storage of carbon in various forms, including carbonate minerals. Over time, these minerals can precipitate out of the ocean water and contribute to the carbonate rock formation on the ocean floor. This process effectively removes carbon dioxide from the atmosphere since the carbon in organic material is either converted into forms that are less likely to re-enter the atmosphere or stored in long-term geological formations.

This natural process is essential in the global carbon cycle, where it counters the effects of carbon release from other human activities, such as burning fossil fuels, which increases atmospheric carbon levels, or the growing use of automobiles that emits carbon dioxide as a byproduct. Fertilizing crops may influence carbon absorption and agricultural productivity but does not directly lead to a significant decrease in atmospheric carbon levels in the way that natural decomposition and carbonate rock formation does.