A. umbilical cord is the answer
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Global warming is the increase in the Earth's temperature caused by the buildup of greenhouse gases in the atmosphere such as carbon dioxide, methane, and nitrogen. The absorbed energy warms the atmosphere and the surface of the Earth.
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Urea is the cellular waste product that the kidneys remove from the blood.Kidneys are the two bean shaped organs that has several functions to keep the body healthy. It not only removes urea from the blood, but also helps in the formation of urine and maintaining the fluid level of the body. The two kidneys are placed on the two sides of the spinal cord. The blood enters the kidney through the renal artery. The nephron within the kidneys mainly take out the waste products and the excess water from the blood and purifies it.If the kidneys of a person fail to work properly then it becomes important to perform dialysis for taking out the waste materials from the blood.
The remains of fossils give scientists clues as to what the world may have been like a long tome ago. If fish fossils are found on the side of a mountain, there may have been a lake there. If a skeleton is found, they can decide what creature it was.