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: Gynaecology & Obstetrics
[{'content': 'Target magnesium level when used for eclampsia prophylaxis \nSelect and explain. \nA. 4.8 → 8.4 mg / dL, B. 2.0 → 4.0 mg / dL, C. 8.4 → 10.0 mg / dL, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Serum magnesium levels are measured at 4\xa0→ 6 hour and adjusted to maintain levels between 4 and 7m Eq / L .', 'role': 'assistant'}]