Which of the following factors is favourable for the formation of oxyhaemoglobin in the alveoli of human lungs?

The toxic effect of carbon monoxide is due to its greater affinity for haemoglobin as compared to oxygen, approximately by (in $\times$)

Assertion : Oxyhaemoglobin dissociates near the organ tissue due to Bohr effect and oxygen is released.
Reason : Increased $CO_2$ concentration reduces the affinity of haemoglobin for oxygen.

Blood analysis of a patient reveals an unusually high quantity of carboxyhaemoglobin content. Which of the following conclusions is most likely to be correct?

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.

Bulk of carbon dioxide $(CO_2)$ released from body tissues into the blood is present as