Carbon dioxide is transported in the blood to the lungs in the form of:

With reference to the oxyhaemoglobin dissociation curve,select the $INCORRECT$ statement/statements.
$I$. $100\%$ saturation is very common.
$II$. $95-97\%$ saturation takes place at $ppO_2 = 100 \text{ mm Hg}$ in alveoli.
$III$. At $30 \text{ mm Hg}$ of $ppO_2$,only $50\%$ saturation can be maintained.
$IV$. The oxyhaemoglobin dissociation curve is $J$-shaped.
Select the correct option.

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:

Identify the incorrect statement regarding the transport of oxygen:

Select the correct option:
$(1)$ Approximately $97\%$ of $O_2$ is transported by plasma / RBCs.
$(2)$ The primary site of gas exchange is alveoli / bronchioles.

$CO$ is more toxic than $CO_2$ because....