Can someone please answer quick and correctly thxs and I will give brainliest

What initially causes a nerve impulse? release of enzymes out of the neuron movement of chemicals into the dendrites of the neuron pathogens attacking the dendrites of the neuron red blood cells bathing the neuron

What's the waste product of electrons and pyruvate combining in fermentation?  

When ash and dust begin to settle on the ground, they eventually become compacted by