Answer:
Environmental Tobacco Smoke
Nearly 99% of the mass of your human body consists of just 6 chemical elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Another 5 elements make up most of the last percentage point: potassium, sulfur, sodium, chlorine, and magnesium.
Answer:
Like with fingerprints, no two people have the same brain anatomy, a study has shown. This uniqueness is the result of a combination of genetic factors and individual life experiences. Like with fingerprints, no two people have the same brain anatomy, a study by researchers of the University of Zurich has shown.
You didn't really provide any possible answers here. However, it's very easy to say that the responsible actors for impulse transmission across the synapses from one nervous cell to another nervous cell is what we call neurotransmitters. These are special molecules that can have different effects when binding onto the required receptor sites.