The following are multiple choice questions (with answers) about medical knowledge.   **Question:** A patient presents with ascending muscle weakness for 2 days. On examination, the limb is flaccid. What investigation should be done first?   (A) Serum potassium   (B) Serum creatinine   (C) Serum magnesium   (D) Serum calcium
['(A) Serum potassium <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Serum potassium \n (B) Serum creatinine \n (C) Serum magnesium \n (D) Serum calcium <> possible answers', '  A patient presents with ascending muscle weakness for 2 days. On examination, the limb is flaccid. What investigation should be done first? <> context@']