Ice floats in water because
A. it has more mass and less volume than water
B. it has less mass and less volume than water
C. it has the same mass and greater volume than water
D. it has the same mass and less volume than water

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 .