Which best describes nitrogen fixiation
A. Nitrogen fixiation is the process of creating free nitrogen for plants to absorb.
B. Nitrogen fixiation is the breakdown of nitrogen in the soil.
C. Nitrogen fixiation is the conversation of nitrogen gas into a usable form.
D. Nitrogen fixiation is the destruction of the bonds between nitrogen and other elements.

C.

Explanation:

Nitrogen fixation is a process by which molecular nitrogen in the air is converted into ammonia or related nitrogenous compounds in soil. Atmospheric nitrogen is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms.

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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true is the final answer!