Why are red blood cells macrocytic in pernicious anemia?A. Production of hemoglobin is impaired, so the erythrocytes are more pale than usual.B. Erythrocytes are produced more rapidly, so the erythrocytes are smaller than usual.C. Normal cell growth but slower cell division in the bone marrow makes the erythrocytes larger than usual.D. Lack of erythropoietin causes sluggish activity of bone marrow and makes the erythrocytes darker than usual.