Answer: Photosynthesis, respiration, decomposition, and combustion.
- A Mainly the process of photosynthesis occurring in green plants
- B Mainly the process of cellular respiration in living organisms
- C Photosynthesis, respiration, decomposition, and combustion
- D Mainly the slow fossilization of buried organic remains over geologic time
Correct answer: C. Photosynthesis, respiration, decomposition, and combustion
Explanation: Carbon cycle: photosynthesis fixes CO<sub>2</sub>; respiration and combustion release CO<sub>2</sub>; decomposition recycles carbon in dead matter.
Energy pyramid showing a simple food chain (producer to herbivore to carnivore) with energy decreasing roughly tenfold at each trophic level.
Concept context
Ecosystems, food chains, energy flow, nutrient cycles, biodiversity, and conservation.