Read passage 3 and answer the questions following the passage. 1 Erythrocytes are red blood cells. 2 They make up the majority of the cells found in human blood. 3 The volume in a cubic milliliter of blood contains more than four million of them and only thousands of the other blood cells. 4 The function of red blood cells is essential to life. 5 Erythrocytes travel continuously through the body's veins and capillaries. 6 As they circulate, they carry oxygen and carbon dioxide between the lungs and the other living cells. 7 They move oxygen to cells and carbon dioxide away from them. 8 The constant exchange of gases is vital since it keeps the body tissues alive and functioning, An essential pigment in erythrocytes enables oxygen to combine with them. 10 This pigment, hemoglobin, also produces the red color of blood. 11 The amount of hemoglobin in red blood cells influence the amount of oxygen they carry. 12 Abnormal levels of hemoglobin affect 'oxygen delivery to the tissues, which hinders the body's functions. 13 The type of hemoglobin in red blood cells also affect their function. 14 For example, sickle cell disease produces high levels of an abnormal hemoglobin. 15 This genetic malady prevents erythrocytes from freely moving through veins and capillaries and carrying oxygen effectively, 16 As cells, erythrocytes are unique. 17 They both generate and develop in the bone marrow along with other cell, but they have no nucleus. 18 Other blood cells include this dense internal component that contains genetic material. 19 Erythrocytes lose their nucleus as they mature, before the marrow releases them to circulate through the bloodstream. Where is the best place to add the following paragraph? During the last seven months of, 'gestation, developing babies' marrow produces fetal hemoglobin. This hemoglobin is called hemoglobin F. Hemoglobin A, adult hemoglobin, starts to replace hemoglobin F a few weeks before birth.