This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood Physiology, Subject name: Physiology
Plasma is a Newtonian fluid because: 
Select and explain. 
A. Viscosity is directly propoional to shear stress, B. Viscosity is equal to shear stress, C. Viscosity is inversely related to shear stress, D. Viscosity is independent of shear stress
D: Viscosity is independent of shear stress
Answer: D: Viscosity is independent of shear stress 
Explanation: For a Newtonian fluid, viscosity remains constant, independent of the shearing force. Whole blood is a non-Newtonian fluid; its viscosity goes changing with the changes in shearing force.