$100 \ ml$ of oxygenated blood contains:

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.

Which of the following is true regarding the transport of $CO_2$ by red blood cells $(RBCs)$ in humans?

What is true about $RBCs$ in humans?

Carbonic anhydrase is found in .......... .

Under which condition,dissociation of oxygen from oxyhaemoglobin in tissues occurs?