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
True about body fluid osmolarity ? 
Select and explain. 
A. Major contributor is proteins, B. Major contributor is Na+, C. ECF osmolarity is 250 mOsm/L, D. Measured by dilution method
B: Major contributor is Na+
Answer: B: Major contributor is Na+ 
Explanation: Ans. is 'b' i.e., Major contributor is Na+