Answer: The cardiovascular System
Step-by-step explanation:
The cardiovascular system homes the heart. The heart is a pump that circulates oxygen and blood throught your body essentially keeping you alive. Without the heart your brain would be dead because your brain would not be getting enough oxygen to funtion. So, although the brain and spinal cord are very important the heart is also if not more for it is the only way you live. You can be brain dead and still alive but not heart stopped and alive.
I hope this helps!