Becky has been asked to provide an example of how carbon is converted from a living form to a non-living form. Which example should she use?
O Carbon dioxide in the atmosphere is absorbed by an ocean.
O Sugar in animals is converted into carbon dioxide during cellular respiration
O Calcium carbonate in rocks is converted into sediment through weathering
O Carbon dioxide from the air is converted into sugars during photosynthesis.

The kidney filters potentially toxic substances in the blood, and thus “clears” the blood of those substances. this clearance function is dependent upon and proportional to the diffusion gradient of the substance across filtering capillaries, i.e. if the concentration of the substance is doubled, twice as much will be cleared from each ml of blood that is filtered. suppose that the body produces a constant amount of a substance x per unit of time. the kidneys eliminate substance x at a rate directly proportional to the concentration of the substance and the volume of blood cleared each minute (c): elimination = c × [x], where [x] is the steady-state concentration of substance x. imagine an individual with an initial concentration of x equal to [x]0 who develops kidney disease. her baseline clearance c0 drops to one half of the original (½c0). what is the new steady state concentration of x? (for simplicity, assume that substance x is 100% filtered by the kidney).