How do producers contribute to the atmospheric carbon balance?

• A. By releasing CO2 during photosynthesis
• B. By removing CO2 from the atmosphere and storing carbon in biomass
• C. By increasing atmospheric nitrogen concentrations
• D. By decreasing water vapor in the atmosphere

Answer: (B)

Producers help regulate atmospheric carbon by taking carbon dioxide out of the air during photosynthesis and storing that carbon in their biomass. In photosynthesis, plants use CO2 and water, with sunlight as the energy source, to build sugars that become plant tissues—leaves, stems, roots, and even wood. That carbon is thus moved from the air into living biomass and can remain stored for long periods in wood, roots, and soil organic matter. The amount stored depends on plant growth and ecosystem conditions, while some carbon returns to the atmosphere later through respiration, decomposition, or combustion. The other ideas don’t fit this process: photosynthesis uses, not releases, CO2; changing atmospheric nitrogen isn’t about carbon storage; and water vapor levels aren’t directly controlled by how producers manage carbon in biomass.