Hello!
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Your answer will be right here!
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Hope this helps!
The right answer is vein (it contains blood and has valves).
The infra-cardiac veins of small and medium caliber possess this system of fight against gravity. The valves consist of a dense connective tissue, surmounted by endothelial cells, corresponding to a fold of the intima. They allow blood circulation in the sense organ / heart but prevent venous reflux.
It has to be a, b or d then.
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Answer:
A.
Explanation:
because the gravity will drop
