Answer: B. Closed
In a closed circulatory system is the one in which the blood is circulated to all the parts of the body of the organism through vessels of different length and width. In this system the blood is pumped from the heart through blood vessels where it is transported to different organs and cells of the body instead of filling up the body cavity.
Forest fires promote regrowth, clear cut has to be replaced
Answer:
The valves' main job is to keep the blood moving in one direction – back up towards the heart. When the valve is open, blood freely flows upward towards the heart and when the valves are closed, blood cannot flow back
Answer:
Guanine
Explanation:
C and G
T and U both go together in DNA.