Oxyhemoglobin acts as which of the following?

Approximately $97\%$ of $O_2$ is transported by $RBCs$. The remaining $3\%$ is transported by:

Oxy-haemoglobin dissociates into oxygen and deoxy-haemoglobin at

How much $CO_2$ is added to every $100\,ml$ of blood by the tissues (in $,ml$)?

The ${O_2}$ dissociation curve is:

$I.$ Increased partial pressure of $O_{2}$
$II.$ Increased partial pressure of $CO_{2}$
$III.$ Increased partial pressure of $H^{+}$
$IV.$ Decreased partial pressure of $O_{2}$
All the above situations favour the dissociation of oxyhaemoglobin except: