9. The production of healthy erythrocytes depends upon the availability of __ 1. copper 2.zinc 3. vitamin B12 4. copper, zinc, and vitamin B_(12)

The production of healthy erythrocytes (red blood cells) depends upon the availability of:<br /><br />3. vitamin B12<br /><br />Vitamin B12 is essential for DNA synthesis and proper cell division, which are critical processes in the production of healthy erythrocytes. Copper and zinc, while important for overall health, are not directly involved in the production of erythrocytes.