Final answer:
Photosynthesis is responsible for capturing the largest amount of carbon from the atmosphere as it converts CO2 into organic compounds, which is more than respiration, decomposition, and combustion do.
Step-by-step explanation:
The process responsible for capturing the largest amount of carbon from the atmosphere is B) Photosynthesis. During photosynthesis, plants and other photosynthetic organisms use sunlight to convert carbon dioxide from the atmosphere into organic compounds, primarily glucose, which is a carbohydrate. This process removes a significant amount of carbon dioxide from the atmosphere, which is then incorporated into the biomass of these organisms. In comparison, respiration returns carbon dioxide to the atmosphere, decomposition releases carbon from dead organic material, and combustion, typically of fossil fuels, significantly increases atmospheric carbon dioxide. However, none of these processes sequester as much carbon as photosynthesis does.
In the broader context of the carbon cycle, the oceans also play a crucial role by dissolving atmospheric CO₂ and contributing to long-term carbon storage through the formation of calcium carbonate sediments, which over geological time can become sedimentary rocks like limestone, representing a massive carbon reservoir. Nonetheless, in terms of immediate carbon capture from the atmosphere among the processes listed, photosynthesis stands out as the most substantial.