The plays a central role in the circulatory system. it consists of four : two for receiving blood and two for pumping blood. a. kidney, veins b. heart, chambers c. heart, veins d. kidney, chambers

Heart pumps blood to your body and it has four chambers. Two Atriums and Two Ventricles.

   -hope this helps .

Well if you pick a machine to work on and that's gonna be your exercise if you don't stick to that machine your muscle strength your muscle mass rather will change because you haven't been doing it you change something in your exercise routine which changes your body's form of dealing with things for example you might become weaker or stronger depending on what kind of exercises you do in whether or not the machine you picked actually your muscles grow.