An instrument that can detect the presence of an electric charge is an

this allows people to make the best decision or pursue the best option. when alternatives are weighed using their advantages and disadvantages, the option whose disadvantages outweigh the advantages (based on a qualitative or quantitative analysis) are shunned while those whose advantages outweigh their disadvantages are pursued.  

positive reinforcement? ?

beta is electron from nucleus

something from nucleus has changed, but charge must be same for cons of charge

your answer is, orbit around the nucleus