Physiology Red cell volume can be measured by injecting tagged red blood cells. All of the following are used to tag red cell, EXCEPT: A 51 Cr B 59 Fe C 32 P D 121 I 💡 Explanation Red cell volume can be measured by injecting tagged red blood cells. All of the following are used to tag red cell, EXCEPT: ✓ Correct Answer: D. 121 I