Why is Anton van Leeuwenhoek considered the "father of microscopy?" A: He was the first person to observe an animal cell through a microscope.
B: He invented the first microscope.
C: He was the best microscope-maker of his time
D: He published an instruction book on how to make microscopes.

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 .