Which process is an example of a chemical change?
a. a metal railing rusting in damp weather
b. a piece of the wood shrinking as it dries out
c. steam rising from a boiling pot of soup
d. alcohol evaporating from a cotton swab

D alcohol evaporating from a cotton swab

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 .