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': 'Which of the following best explains why Lignocaine has a higher fetal-to-maternal plasma ratio when compared with bupivacaine? \nSelect and explain. \nA. Bupivacaine has low molecular weight, B. Lignocaine has higher protein-binding, C. Bupivacaine has a lower dissociation constant (pKa), D. Lignocaine is less protein bound', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Lignocaine is\xa0 less protein bound than bupivacaine. Unbound form of drug thus easily gets transferred across placenta.', 'role': 'assistant'}]