A/E are the features of exercise:-

Ans. is 'a' i.e. left shift of Hb-O2 dissociation curve A right shift of Hb-Oz dissociation curve is seen in exercising muscles.During exercise, the contracting muscles need more O2 for energy production.This need in meet by increasing the blood supply to the muscles. Cardiac activity increases to increase the stroke volume. Capillary bed of the contracting muscle dilates and many previously closed capillaries open up.In contracting muscle the amount of O2 extracted from blood increases (There is a net 3 fold increase in O2 extraction from each unit of blood). This is because of right shift of Hb-O2 dissociation curve.Right shift of Hb-O2 dissociation curve occurs because of -Accumulation of CO2 (Decrease pH)*Increased temp, of contracting muscles*Rise in RBCs 2,3 - DPG-*