This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
Which is not a RBC membrane protein? 
Select and explain. 
A. Ankyrin, B. Nebulin, C. Spectrin, D. Gycophorin
B: Nebulin
Answer: B: Nebulin 
Explanation: The protein skeleton consists of 2D mesh of spectrin tetramers and oligomers. It is attached to RBC membrane by attaching to ankyrin. Membrane proteins like glycophorin also present. Ref: Textbook of medical physiology by N Geetha, 3rd edition, page no. 77