Why are the carbon cycle, the phosphorous cycle, the water cycle, and the nitrogen cycle all considered to be biogeochemical cycles? because all these cycles include the organisms inhabiting water, land, and air. because all these cycles include living organisms, the biosphere, and the chemical factors in them. because all these cycles include nonliving organisms, the atmosphere, and the physical factors in them

The correct answer is- Because all cycles of these elements include living organisms, the biosphere, and the chemical factors that are present them.

A biogeochemical cycle can be described as the cycling of chemical substances through the biotic ( that includes the living forms, which is present in the biosphere) and abiotic ( that includes the non living parts, which lie in the lithosphere, atmosphere, and hydrosphere compartments of Earth) component.

The cycling of phosphorous, water, nitrogen, and carbon occurs through living and non living compartments of earth.

Thus, they are considered as biogeochemical cycle.

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.  

read more on -

the answer is b.) hydrogen bonds between bases.