Iron combines with oxygen and water from the air to form rust. If an iron nail were placed in a beaker and allowed to rust for a month, one should find that the rusty nail weighs:

Distance and velocity graph

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 .

The answer is conduction