Exposure to carbon monoxide (from coal gas) is extremely dangerous and can kill a patient because
A. The compound carboxyhaemoglobin (COHb) it forms with heamoglobin can gradually clot the blood resulting in circulatory failure
B. COHb reduces the ability of blood for transport oxxygen by ruputring a vast majority of erythrocytes
C. COHb greatly modifies the structure of haemoglobin, thus makiing it lose its affinity for oxygen
D. None of the above