Answer:
We call it
Double circulation bcoz their are 3 circulation exist between heart, lungs and body organs.
EXPLANATION :
Flow of blood is left to right
1. Pulmonary circulation
<em>Right</em><em> </em><em>ventricle</em><em> </em><em>-</em><em>pulmonary</em><em> </em><em>artry</em><em> </em><em>-</em><em> </em><em>lungs</em><em> </em><em>-</em><em> </em><em>pulmonary</em><em> </em><em>veins</em><em> </em><em>-</em><em> </em><em>left</em><em> </em><em>artria</em><em> </em>
2. Systemic circulation
Left ventricle - systemic artry - body organs - systemic veins- right artria
I looked it up and it is C
They saw how smoking effected the body since smoking was pushed as something good for a long time, a lot of people started smoking and after a few years doctors finally saw a difference between a smokers body and a non smokers body