Consider the demographics for two countries one with a low income almost impoverished population they other an economically well off country. What factors listed would contribute to the decline in birth rate and larger +75 population in the high income country? Check all the might apply

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .

The answer is d.potassium