Assess understanding of the carbon cycle: major reservoirs and fluxes (atmosphere, biosphere, oceans, soils, rocks), key processes (photosynthesis, respiration, decomposition, ocean exchange, weathering), timescales, human influences (fossil fuel emissions, land-use change, cement production), feedbacks to climate, and implications for carbon budgets and mitigation; questions may include interpreting diagrams or data and explaining causal links between anthropogenic activities and atmospheric CO2 levels.