Oxyhemoglobin acts as which of the following?

Every $100 \ ml$ of oxygenated blood can deliver around $............$ of $O_2$ to the tissues under normal physiological conditions. (in $ml$)

Approximately how many $mL$ of $CO_2$ is delivered to the alveoli by every $100$ $mL$ of deoxygenated blood?

The following statements refer to the transportation of gases. Read them carefully and choose the correct option containing the incorrect statements.
$(i)$ After leaving the lungs, each litre of blood contains about $20 \ ml$ of oxygen.
$(ii)$ When $PCO_2$ rises, the affinity of haemoglobin for oxygen is increased.
$(iii)$ Each litre of arterial blood contains about $4 \ ml$ of $CO_2$.
$(iv)$ The role of oxygen in the regulation of respiratory rhythm is quite significant.

What happens to the oxygen-hemoglobin $(O_2-Hb)$ dissociation curve when the temperature decreases?

At which level does the following reaction occur?
$H^+ + HCO_3^- \rightarrow H_2CO_3 \rightarrow H_2O + CO_2$