Although pulmonary vein carries oxygenated blood still it is known as vein not artery. Give reason.
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https://www.meritnation.com/ask-answer/question/why-cant-call-a-pulmonary-artery-as-vein-and-pulmonary-vein/transportation-in-animals-and-plants/9762819
https://www.meritnation.com/ask-answer/question/why-cant-call-a-pulmonary-artery-as-vein-and-pulmonary-vein/transportation-in-animals-and-plants/9762819