In the tundra, life forms are limited by the interaction of several of Earth's spheres. One sphere that interacts with both the geosphere, hydrosphere, and biosphere is the cryosphere. What is this sphere responsible for in the tundra?
A) poor, rocky soil
B) low growing plants
C) ground permafrost
D) mountainous terrain

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 .