Final answer:
Erythroblasts usually account for 80% to 90% of the erythroid cells in bone marrow.
Step-by-step explanation:
In bone marrow, erythroblasts usually account for 80% to 90% of the erythroid cells. Erythroblasts are the precursor cells of red blood cells (erythrocytes) and are responsible for their production. They undergo several stages of maturation before becoming fully functional red blood cells.