The bulb of a thermometer is placed in your mouth. Which of the following explains why the level of the liquid rises in the thermometer? A. Hot air rises inside the thermometer.
B. Heat energy changes into light energy.
C. The liquid expands when heated.
D. Heat can change a solid into a liquid.

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 .