Question

1. what happens when fossil fuels are burned for energy? a. carbon stored in them is released as carbon dioxide. b. carbon is converted into sedimentary rocks. c. carbon is absorbed by the oceans. 14. how have human activities impacted the carbon cycle? a. by decreasing the levels of carbon dioxide in the atmosphere b. by increasing the levels of carbon dioxide in the atmosphere through the burning of fossil fuels c. by trapping carbon dioxide in sedimentary rocks 15. what natural process contributes to the sudden release of large amounts of carbon dioxide into the atmosphere? a. photosynthesis b. volcanic eruptions c. oceanic uptake 16. what is the main process by which carbon is returned to the soil as nutrients? a. photosynthesis b. decomposition c. sedimentation

Explanation:

1. Fossil fuels contain carbon. When burned, they react with oxygen. The chemical reaction releases carbon as carbon dioxide ($\text{CO}_2$).
2. Burning fossil fuels (like coal, oil, gas) releases stored carbon as $\text{CO}_2$. Human activities (e.g., power - plant operations, vehicle use) increase $\text{CO}_2$ levels in the atmosphere.
3. Volcanic eruptions release large amounts of gases, including $\text{CO}_2$, from the Earth's interior. Photosynthesis absorbs $\text{CO}_2$, and oceanic uptake is a slower process.
4. Decomposition is when organic matter (dead plants, animals) breaks down. Microorganisms convert carbon - containing compounds into nutrients for the soil. Photosynthesis takes in $\text{CO}_2$ and produces organic matter, and sedimentation is related to the settling of particles.

Answer:

1. A. Carbon stored in them is released as carbon dioxide.
2. B. by increasing the levels of carbon dioxide in the atmosphere through the burning of fossil fuels
3. B. volcanic eruptions
4. B. decomposition