Haemoglobin (Hb) transports oxygen from the lungs to tissues. The partial pressure of the oxygen in lungs is different from that tissues. Each Hb can bind to up to four oxygen molecules. Suppose, we have an equal number of Hb and oxygen molecules and all the oxygen molecules are in bounded form. Then, which of the following is true
a) Almost all the Hb molecules have one bound oxygen molecule
b) Nearly half of all the Hb molecules are bound to two oxygen molecules
c) Nearly one-fourth of all the Hb molecules are bound to four oxygen molecules each
d) Most of the Hb molecules have one bound oxygen molecule each; the rest either have no bound oxygen or have two or more bound oxygen molecules