Indicate the metric unit for: a) mass, b) length, and c) volume

For mass it would be grams. More commonly known as kilograms. Length would be in meters. Also commonly known as kilometers. Last but not least, volume would be in liters. 

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 .

Answer two atoms of oxygen;