An open circulatory system is a system in which the blood is not sealed in arteries and veins, and it can also be directly open to the environment.
A closed circulatory system is a system in which the blood is sealed in arteries and veins and never leave the system.
Analyzing the human circulatory system, we see that the blood is sealed in veins and arteries and never leave the system.
Therefore, the correct answer is B) closed circulatory system
