This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Neuraxial Blockade, Subject name: Anaesthesia
During epidural analgesia the following points suggests that needle is in the extradural space 
Select and explain. 
A. Loss of resistance sign, B. Negative pressure sign, C. Mackintosh extradural space indicator, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Loss of resistance technique, tactile feedback from the needle, and surface landmarks are traditionally used to guide the epidural needle tip into the epidural space (EDS). Number of newer techniques are now available like ultrasound - Ultrasound imaging with preacquired three-dimensional images of spine, Ultrasound through needle, Ultrasound imaging with preacquired three-dimensional images of spine Modifications of the loss of resistance techniqueMembrane in syringe technique, Epidural balloon, Epidrum, Episure Autodetect, Auditory and visual display of pressure wave