Which part of the Sun's electromagnetic spectrum has the longest wavelength?
1radio wave radiation
2infrared radiation
3visible light radiation
4X-ray radiation

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 .