Answer:
We call it
Double circulation bcoz their are 3 circulation exist between heart, lungs and body organs.
Step-by-step explanation :
Flow of blood is left to right
1. Pulmonary circulation
Right ventricle -pulmonary artry - lungs - pulmonary veins - left artria
2. Systemic circulation
Left ventricle - systemic artry - body organs - systemic veins- right artria