Where did the water on earth come from? a. mainly volcanic eruptions b. probably from a combination of sources c. probably from the nebula that formed the planet d. mainly comets and asteroids ! science!

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).

Which are evidence of seafloor spreading? check all that apply. molten material magnetic stripes continent material drilled core samples ocean water samples

Which of the following types of pollution is most responsible for large numbers of deaths worldwide because of unsafe drinking water? (a) nutrient pollution (b) thermal pollution (c) pathogen pollution (d) sediment pollution