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
Ineffective osmols is 
Select and explain. 
A. Na+, B. K+, C. Urea, D. All
C: Urea
Answer: C: Urea 
Explanation: Some osmoles do not exert osmotic pressure as they freely cross through a membrane. These are ineffective osmoles. Eg: Urea, Glucose.