Which one of the following air pollutants has a very strong affinity towards haemoglobin (Hb) of blood?

Carbon monoxide binds to haemoglobin far more strongly than oxygen, forming carboxyhaemoglobin.

Carbon dioxide is carried by blood but does not lock onto haemoglobin with such affinity.

Sulphur dioxide mainly irritates the respiratory tract rather than binding haemoglobin.

Nitrogen dioxide also attacks the lungs instead of gripping haemoglobin.

The exceptionally tight bond of carbon monoxide starves tissues of oxygen.

Its affinity for haemoglobin is roughly two hundred times that of oxygen.