Asubstance that enters earth's cycles and does harm to living things is
a. a pollutant.
b. freshwater.
c. hydrogen.
d. oxygen.

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

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in case if a person is bitten by a snake then after contacting the medical control, there is a need to apply a pressure immobilization bandage and try to make the person calm and as still as possible unless and until any medical comes.

try to avoid washing of the bitten region as any venom left on the skin can in determining the snake. make sure to not cut the wound, or try to suck the venom out from the region, and do not apply any kind of tourniquet.