In blood,the majority of $CO_2$ is transported by which of the following?

People living at sea level have around $5 \; million$ $RBCs$ per cubic millimetre of their blood,whereas those living at an altitude of $5400 \; m$ have around $8 \; million$. This is because at high altitude:

How many $O_2$ molecules can bind with a single molecule of $Hb$?

Which protein is essential for the transport of $O_2$?

$CO_2$ is carried by haemoglobin as carbamino haemoglobin. This binding of $CO_2$ with $Hb$ is related to the partial pressure of .........

Carbon dioxide entering the red blood cells reacts with water to form carbonic acid. Which enzyme is responsible for this reaction?