Assess students' understanding of major carbon reservoirs (atmosphere, biosphere, oceans, soils, lithosphere) and key fluxes (photosynthesis, respiration, decomposition, ocean exchange, sedimentation, volcanic outgassing) plus human perturbations (fossil fuel combustion, land-use change, cement production). Test ability to compare reservoir sizes and flux magnitudes qualitatively, trace carbon pathways, explain residence times and feedbacks, and link flux imbalances to rising atmospheric CO2 and climate impacts. Scope: Grades 9–12, medium difficulty.