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: Anaesthesia
[{'content': 'Epidural anaesthesia is initiated in Primigravida at 38 weeks gestation, with a bolus of 15mg of Bupivacaine. Within few minutes, fetal heart rate monitoring shows variable decelerations. If scalp pH reveals fetal acidosis, compared with a normal pH, the anaesthetic absorbed by fetus will be present in \nSelect and explain. \nA. Lower concentration, most in ionized form, B. Higher concentration, most in ionized form, C. Higher concentration, most in unionized form, D. Unchanged concentration, equal fraction of ionized and nonionized', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Local anaesthetics, being basic drugs become more ionized at low fetal pH. Ionized molecules are thus trapped on fetal side of circulation.', 'role': 'assistant'}]