Ans. is 'b' i.e., Supraclavicular Brachial plexus blocko This is the second most commonly practised block after central neuraxial block (spinal & epidural anaesthesia).Brachial plexus block is used for upper limb surgeries.o Brachial plexus can be blocked by 4 approaches : -Interscalene approachBrachial plexus is blocked between anterior and middle scalene. This approach is not used routinely due to close proximity of vital structures. Ulnar nerve is usually spared by this approach because injection is given in close proximity of upper nerve roots and inferior nerve roots (C8-T1) may be spared.This technique provides excellent anaesthesia and analgesia for shoulder and upper arm procedures, (in contrast to other three approaches which do not provide adequate shoulder anaesthesia).Complications include Homer syndrome (due to stellate ganglion block), phrenic nerve block, intravascular injection into carotids and epidural or intrathecal injections.Supraclavicular approachThis is the most commonly used approach. It involves the injection of local anaesthetic in close proximity to the trunks of the brachial plexus by inserting the needle lateral to subclavian vessels. The supraclavicular block is performed where the brachial plexus is most compact, consequently, it produces reliable and rapid onset anaesthesia and is particularly useful in a fast paced ambulatory surgery centre.Pneumothorax is the most common complication. Other complications include phrenic nerve block, intravascular injection in subclavian artery or vein, Homer syndrome, hematoma formation.Infra-clavicular approachInfraclavicular block involves the injection of local anaesthetic in close proximity of cords of the brachial plexus. The axillary nerve may be spared as this nerve exits the brachial plexus sheath proximal to the level of infraclavicular block.Axillary approachAxillary block involves the injection of local anaesthetic in close proximity of terminal branches of the brachial plexus. The major disadvantage of this approach is that mucocutaneous and intercostobrachial nerves are spared. So arm surgery cannot be performed. In contrast to interscalene approach, most intense block occur in (C7-T1) ulnar dermatomes and least in C5-C6 dermatomes.