The answer is pulmonary and systemic circuit
It’s 5 with 3 zeros. Or 5000
I believe it's 1. Duplication of DNA has already happens.
We are all carbon based organisms , so i would say that carbon is the most important element to us and to all living organisms oxygen and hydrogen are important too but...
but every element is really important to all living things , without one Element we can't function a certain organ , like a puzzle , without one piece it wouldn't be right
