Helium decays to form lithium. which equation correctly describes this decay?

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 should be vaporization 

The correct answer would be b) volume versus temperature, because they are also directly proportional.