This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Body fluid compaments, Subject name: Physiology
A 60 kg man has haematocrit of 40%. His plasma volume would be approximately: 
Select and explain. 
A. 2.4 L, B. 2.9 L, C. 3.6 L, D. 5.0 L
B: 2.9 L
Answer: B: 2.9 L 
Explanation: Plasma volume = Total blood volume * (1 - Hematocrit) The total blood volume is about 8% of body weight Blood volume of 60 kg man = 0.08 * 60 = 4.8 L Plasma volume = total blood volume * (1-hematocrit) = 4.8 * (1-0.40) = 4.8 * 0.60 = 2.88 L Also, about 60% of the blood is plasma and 40% is RBCs Thus, plasma = 5% of body weight and haematocrit is 3% of body weight