Blood transports $CO_2$ in which of the following forms?

Which fact suggests that most oxygen is transported from lungs to the tissues combined with haemoglobin rather than dissolved in blood plasma?

$A$: Major part of carbon dioxide is transported in the form of sodium bicarbonate.
$R$: $0.3 \; ml$ of carbon dioxide is transported per $100 \; ml$ of blood in dissolved state in plasma of blood.

With which part of $Hb$,$O_2$ molecules bind?

Identify $A$ and $B$ in the given oxygen-haemoglobin dissociation curve and choose the correct option accordingly.

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.