Choose all the answers that apply. Light
cannot travel through a vacuum
slows down when traveling through denser substances
speeds up when traveling through more dense substances
travels in transverse waves
can be absorbed and transformed into heat

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 .