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': 'A woman in her first pregnancy repos that she smokes one pack of cigarettes a day. An ultrasound is ordered in the thiy second week of the pregnancy to evaluate for which of the following: \nSelect and explain. \nA. Amniotic fluid volume, B. Fetal size, C. Fetal abnormalities, D. Fetal motion', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Fetal size', 'role': 'assistant'}]