This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Interstitial fluid volume can be measure by 
Select and explain. 
A. Tritium oxide - Sodium thiosulfate, B. Inulin - Radioactive sodium, C. Aminopyrine - Sucrose, D. Inulin - Sodium albumin labelled with radioactive Iodine.
D: Inulin - Sodium albumin labelled with radioactive Iodine.
Answer: D: Inulin - Sodium albumin labelled with radioactive Iodine. 
Explanation: Interstitial fluid volume cannot be calculated directly. It is measure as ECF volume. Plasma volume
ECF volume calculated by Inulin. Plasma volume calculated by Serum albumin labelled with radioactive Iodine.