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
Which of the following has lowest Pka value 
Select and explain. 
A. Lignocaine, B. Chloroprocaine, C. Prilocaine, D. Bupivacaine
A: Lignocaine
Answer: A: Lignocaine 
Explanation: Lignocaine has lowest Pkavalue, thus maximum unionised drug at physiological pH. Whereas chloroprocaine has highest Pka value.