Most of the carbon in the rocks that form Earth's mantle and crust was stored there when Earth formed. The rest of Earth's carbon is stored in various reservoirs and exchanged in many ways. In a model of the carbon cycle, which process does NOT contribute directly to the storage of carbon within sediment? A. the deposition of organic carbon from decaying organisms
B. the deposition of dissolved carbon dioxide from the atmosphere
C. the formation of carbon dioxide through metabolism of carbohydrates
D. the formation of fossil fuels from terrestrial organisms under high heat and pressure

The answer is not c

Answerthis solution will not form a precipitateexplanationsolubility equilbrium:         pbf₂(s)  ⇄ pb²⁺(aq) + 2 f⁻(aq)the solubility product expression is    (we exclude solids from the equilibrium expression).now suppose we have the trial ion product q, which we can define as    then, we can interpret  q as the product of the concentration of the ions that we have and ksp as the product of the ion concentrations that are needed to form a saturated solution.if q > ksp, then that implies that there will be a surplus of ions that exceed the amount that is required to form a saturated solution. a precipitate will then form (the precipitate continually  forms until the surplus ions are removed and q is decreased to ksp's value).if q = ksp, the saturated solution that forms is barely saturated and the precipitate will be minimal.if q < ksp, then the ion concentration will not be enough to form a saturated solution (so no precipitate).using our information, we calculate the trial ion product:     since q = 2.7  × 10⁻⁸ < ksp =  4  ×  10⁻⁸, a precipitate will not form.