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
[{'content': 'Which of the following is a polar amino acid? \nSelect and explain. \nA. Tryptophan, B. Serine, C. Valine, D. Tyrosine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Note: Polar amino acids are hydrophilic and nonpolar amino acids are hydrophobic.', 'role': 'assistant'}]