Ants live in the hollow thorns of an acacia tree. The tree provides food and shelter for the ants. The ants protect the tree from
herbivores that might otherwise eat the tree.
Which type of relationship does this represent?
commensalism
predator/prey
mutualism
parasitism

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 .