In a traffic circle, roundabout signs control the traffic. I hope this helps. :)
Answer:
excretory system and circulatory system
Explanation:
Blood is part of circulatory system and as it move through various organs it exchanges the gases i.e give oxygen to the cell and take carbon dioxide from them. After taking CO2, the blood becomes impure and hence it passes through the kidney before going to the heart. Kidney is part of excretory system which removes carbon dioxide from blood and thus purifies it.
Answer:
D
Explanation: the bones can becomew brittle from not haveing calcium
