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: Surgery
In submandibular surgery incision is given 2 cm below the border of mandible to preserve which nerve? 
Select and explain. 
A. Marginal mandibular nerve, B. Mental Nerve, C. Long buccal nerve branch of facial, D. Inferior alveolar nerve
A: Marginal mandibular nerve
Answer: A: Marginal mandibular nerve 
Explanation: The mandibular branches of the facial nerve run parallel to the lower border of the mandible, mostly below it. Of them, the marginal mandibular nerve follows almost exactly the lower border. Hence, to avoid sectioning of this nerve and causing loss of motor supply to lower lip and mentalis, we give the submandibular incision at lest 2 cm of 2-finger width below the lower border of mandible.