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: Biochemistry
Which of the following aminoacids in a protein commonly acts as a potential 0-Glycosylation site for attachment of an oligosaccharide unit: 
Select and explain. 
A. Glutamine, B. Cysteine, C. Serine, D. Asparginine
C: Serine
Answer: C: Serine 
Explanation: C i.e. Serine