Which fact suggests that most \[{{O}_{2}}\] is transported from lungs to the tissues combined with haemoglobin rather than dissolved in blood plasma?

• A. \[{{O}_{2}}\] -carrying capacity of whole blood is much higher than that of plasma and \[{{O}_{2}}\] content of blood leaving the lungs is greater than that of blood entering the lungs.
• B. Haemoglobin can combine with\[{{O}_{2}}\].
• C. Oxyhaemoglobin can dissociate into haemoglobin and\[{{O}_{2}}\].
• D. Increase in \[C{{O}_{2}}\]-concentration decreases the \[{{O}_{2}}\]-affinity of haemoglobin.