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
[{'content': 'Binding site present on β subunit of Na+ - K+ pump is \nSelect and explain. \nA. Na+, B. K+, C. ATP, D. Glycosylation', 'role': 'user'}, {'content': 'Answer: D \nExplanation: β subunit shows three Glycosylation sites extracellularly, with attached carbohydrate residues.', 'role': 'assistant'}]