Earth’s atmosphere is a mixture of oxygen, water vapor, and other gases. helium nitrogen hydrogen carbon

The right answer is nitrogen.

The chemical composition of the atmosphere essentially comprises nitrogen (78%), oxygen (21%), rare gases (Argon, Neon, Helium ...) and in the lower layers, water vapor and carbon dioxide.

The constituents of atmospheric air can be classified into two categories:

* constituents such as nitrogen, rare gases, whose concentration is constant, at least in the lower layers of the atmosphere.

* Constituents whose content varies in the atmosphere, such as carbon dioxide and especially water vapor.

poor water quality affects most estuarine organisms, including commercially important fish and shellfish. the pollutants that have the greatest impact on the health of estuaries include toxic substances like chemicals and heavy metals, nutrient pollution (or eutrophication), and pathogens such as bacteria or viruses.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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