Carbon dioxide affects O2binding to Hb by: a) CO2forming iron carbonate with the heme-iron atom. b) Hb competing with carbonic anhydride for CO2. c) directly binding to heme-Fe in the oxygen binding site of hemoglobin. d) forming HCO3- that combines with H+ to increase CO2binding. e) forming H+ HCO3- where the H is an antagonist to oxygen binding to Hb.