The following are multiple choice questions (with answers) about medical knowledge.   **Question:** At physiological pH, which of these amino acids has a positive charge?   (A) Valine   (B) Aspaic acid   (C) Arginine   (D) Isoleucine
['(C) Arginine <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Valine \n (B) Aspaic acid \n (C) Arginine \n (D) Isoleucine <> possible answers', '  At physiological pH, which of these amino acids has a positive charge? <> context@']