The solar system likely began as a huge cloud of gas and dust. the force that most likely caused this cloud to form the large clumps that became the sun and planets is

The answer is Gravity.

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 .