<prompt> Haldane effect is:Effect of O2 on CO2 carriage in bloodEffect of CO2 on O2 carriage in bloodEffect of PCO2 on CO2 carriage in bloodEffect of pH on oxygen carriage in blood  <response>: In the tissues, Hb unloads its oxygen and takes up CO2. CO2 enters red cells and combines with water to form H2CO3. CO2 H2O - H2CO3 - H HCO3- The H ions are taken up by the Hb to form HHb; it is aided by the fact that deoxyhemoglobin is a better acceptor of H. Also, deoxyhemoglobin more readily forms carbamino compounds. In lungs, the reactions are reversed. The inhaled O2 combines with Hb. Oxyhemoglobin is a better donor of H; H is now released by Hb. H combines with HCO3- to form H2CO3. H2CO3 - CO2 H2O. CO2 will be exhaled out. Thus, unloading of O2 in peripheral capillaries facilitates the loading of CO2, and oxygenation, in the lung-enhances the unloading of CO2. This has been termed Haldane effect. Option A is correct. 