(i) Though pulmonary artery carries carbon-dioxide rich blood, it is still called as artery and not vein.
(ii) Arteries have thick, elastic walls.
(iii) Blood of all humans are red in colour.
(ii) Since the blood flow through arteries rapidly at high pressure, the arteries have thick elastic walls.
(iii) The red blood cells contain a red pigment called haemoglobin. The presence of haemoglobin makes blood appear red.
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