Which blood vessel does not carry any carbon dioxide ?

In which of the following vertebrate group/groups, heart does not pump oxygenated blood to different parts of the body ?

Which vein brings clean blood from the lungs into the heart?

It has been found that people living in very high mountains have many more red corpuscles in their blood than people living in plains. Which one of the following best accounts for this phenomenon?

The phloem tissue in plants is responsible for the transport of :