<s>[INST] context: Long thoracic nerve (C5-C7): It branches off the C5-C7 roots, descends posteriorly to the roots of the plexus and the axillary aery and along the lateral surface of the serratus anterior muscle, with the lateral thoracic aery, while supplying the muscle. The long thoracic nerve is one of the few nerves found superficial to the serratus anterior muscle. Phrenic nerve (C3-C5): Courses veically along the anterior scalene muscle between the subclan aery and the subclan vein en route to innervate the diaphragm. ("C3-C5, keep the diaphragm alive" is a mnemonic that is used to remember the spinal nerve levels of the phrenic nerve.) Transverse cervical nerve (C2-C3): Innervates the skin over the anterior pa of the neck. Supraclavicular nerve (C3-C4): Innervates the skin over the lower poion of the neck, upper pa of the chest, and the shoulder. Also Know:Erb's palsy (brachial plexus bih injury) is caused by a stretch injury of the brachial plexus that occurs during a difficult bih, specifically to nerve roots C5 and C6 and sometimes C7.Klumpke's palsy results from injury to the inferior trunk of the brachial plexus. The intrinsic muscles of the hand are affected and a "claw hand" may result. [/INST] question: What is the root value of long thoracic nerve? | options: A: C3 4 5 B: C5 6 7 C: C7 8 T1 D: C2 3 4 | answer: B </s>