Which of the following will allow nitrogen fixation to occur? a: photosynthesis b: decay c: bacteria d: conversion of hydrogen

The correct answer is option C, that is, bacteria.  

Lightning produces a comparatively minute concentration of ammonia. However, the foremost transformation of nitrogen to ammonia is done by the microorganisms in the process known as nitrogen fixation.  

All the nitrogen-fixing species are bacteria. Some of them live unconventionally from other organisms, thus also known as free-living nitrogen-fixing bacteria. Others live in close symbiotic relationships with plants or other species. The examples of nitrogen-fixing bacteria are Azotobacter and Cyanobacteria.  

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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