A gas has a volume of 800.0mL

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 .

B"hf and f-"  is the correct answer took the test on edgenuity and got it right     

Your question is not clear but if you can explain yourself i would be glad to .  just trying to : ))