Catalysts affect the chemical reactions that take place within the body. what function do catalysts perform in chemical reactions?
a. catalysts slow down the rate of chemical reactions.
b. catalysts are always formed by chemical reactions.
c. catalysts are used up during a chemical reaction.
d. catalysts lower the activation energy of a chemical reaction

I think the best answer for this is D.  Catalysts lower the activation energy of a chemical reaction. Catalyst is a substance that speeds a chemical reaction. It is not consumed as the reaction proceeds. A catalyst offers a new route for faster reaction.

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 .