!PLEASE HELP ASAP! what is the half-life of the radioactive isotope? what mass of the radioactive isotope will be left after three(3) half-lives?

Which of the following may one conclude from a map that shows the average ph value of rainfall in the u.s.? acid rain is a more serious problem on the east coast. acid rain falls equivalently across the continental u.s. there are more factories on the west coast. the midwest has fewer forests than the rest of the u.s.